8,8-Dimethylhexahydro-3A,6-Methano-2,1-Benzothiazole 2,2-Dioxide
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HS Code |
235237 |
| Chemical Formula | C11H17NO2S |
| Molecular Weight | 227.32 |
| Appearance | Typically a solid (physical state may vary depending on conditions) |
| Odor | May have a characteristic odor (specific details may require experimental determination) |
| Stability | Stability may vary depending on environmental factors such as temperature, light, and presence of reactive substances |
| Hazard Class | Hazard classification would need to be determined based on factors like toxicity, flammability, etc. (no data provided) |
As an accredited 8,8-Dimethylhexahydro-3A,6-Methano-2,1-Benzothiazole 2,2-Dioxide factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 1 kg of 8,8 - Dimethylhexahydro - 3A,6 - Methano - 2,1 - Benzothiazole 2,2 - Dioxide in sealed chemical - grade packaging. |
| Shipping | 8,8 - Dimethylhexahydro - 3A,6 - Methano - 2,1 - Benzothiazole 2,2 - Dioxide is shipped in sealed, corrosion - resistant containers. Special handling per safety regulations for chemicals ensures secure transport to prevent spills and exposure. |
| Storage | Store "8,8 - Dimethylhexahydro - 3A,6 - Methano - 2,1 - Benzothiazole 2,2 - Dioxide" in a cool, dry, well - ventilated area away from heat sources, ignition sources, and incompatible substances. Keep it in a tightly - sealed container to prevent moisture absorption and potential reactions. Store it separately from oxidizing agents and bases to ensure safety. |
Critical Control of Exotherm Propagation in Large-Scale Epoxy CastingsIn the manufacture of epoxy-insulated dry-type distribution transformers and instrument transformers, the gelation phase of anhydride-cured cycloaliphatic epoxy systems is prone to generating a steep, uncontrolled exothermic front that propagates through the bulk volume of a casting weighing in excess of 200 kg. When the internal temperature overshoot exceeds the glass transition temperature of the partially cured matrix by more than 15 °C, irreversible microcracking initiates at the coil-winding interface and propagates along the stress-concentration paths around copper conductors. Mitigation of this failure mode is achieved through the incorporation of 8,8-dimethylhexahydro-3a,6-methano-2,1-benzothiazole 2,2-dioxide as a latent accelerator that remains dormant below a specific triggering temperature. The compound is pre-dispersed at an addition level of 0.8–3.0 phr (relative to epoxy resin weight) into the degassed resin component prior to blending with the anhydride hardener in a static mixer fitted with a 21-element helical insert. Processing is conducted on a twin-component vacuum casting station with automatic volumetric dosing; material residence time in the mixing head must remain below 45 s because the latency threshold is kinetic, not purely thermal, and prolonged shear-induced activation can reduce the pot life from a targeted 72 h at 35 °C to under 8 h. After vacuum-assisted filling of the mould at 60–70 °C, the curing cycle is programmed as a ramp of 10 °C/h to 90 °C, a soak of 4 h, followed by a post-cure step to 130 °C. In-process thermal monitoring via embedded thermocouples confirms that the exotherm peak is blunted to a ΔT of no more than 22 °C, whereas unmodified systems routinely exhibit ΔT values exceeding 48 °C. Finished castings are subjected to partial discharge testing according to IEC 60270 and thermal class evaluation per IEC 60085. The end-product delivered is an encapsulated winding block for distribution transformers rated up to 36 kV, compliant with IEC 60455-3-5 resin specifications and the flammability requirements of UL 94 V-0. Operational boundaries: the latent character is fully exploited only when the anhydride-to-epoxy stoichiometric ratio is maintained between 0.85 and 0.95; ratios outside this band interact with the sulfonamide-dioxide activator in ways that either prematurely initiate crosslinking during compounding or leave unreacted accelerator residues that plasticise the network, reducing the heat deflection temperature measured under ISO 75-2 Method A by as much as 18 °C.Powder coatings formulated with a hybrid polyester-epoxy resin backbone and intended for automotive under-hood aluminium heat shields must reconcile two contradictory demands: extended storage stability of the extruded chip at ambient warehouse conditions in tropical climates, and rapid snap-cure at peak metal temperatures below 170 °C to avoid thermal distortion of the thin-gauge substrate. Standard imidazole-accelerated systems exhibit a critical trade-off, with 1.5 wt% 2-methylimidazole delivering an acceptable gel time of 90 s at 160 °C but showing a catastrophic increase in pellet sintering temperature from 48 °C to 62 °C after 14 days of accelerated storage at 40 °C and 85% relative humidity. The 8,8-dimethylhexahydro-3a,6-methano-2,1-benzothiazole 2,2-dioxide latent accelerator is introduced at a concentration of 1.2–4.0 wt% on total resin solids and is incorporated during the melt-mixing stage on a co-rotating twin-screw extruder with a 26:1 L/D ratio, barrel zone temperatures set to a flat profile of 95–105 °C. Screw geometry employs two sets of kneading blocks upstream of the additive feed port to ensure that the sulfonamide dioxide is wetted into a dispersion with a Hegman gauge reading finer than 15 µm before the melt is discharged onto a chilled roll. The extrudate is subsequently milled and classified to a particle size distribution of D50 = 32–38 µm. Electrostatic spray application onto a phosphated aluminium substrate at a film build of 60–80 µm is followed by cure in a direct gas-fired oven with a dwell time of 5.5–8.0 min and a part surface temperature of 155–165 °C. The latent nature of the accelerator prevents premature reaction in the extruder, and stability data under ISO 8130-8 storage conditions confirm no increase in the pellet blocking coefficient after 28 days at 40 °C. The cured film must pass a 500 h continuous salt spray test per ISO 9227 with less than 1.5 mm underfilm corrosion creep at the scribe, and withstand thermal shock cycling of 300 cycles from −40 °C to 160 °C without loss of adhesion tested under ISO 2409. End-use products include engine compartment heat shields and battery tray insulators for electric vehicles, manufactured under the IATF 16949 quality management framework and subject to REACH (EC 1907/2006) and RoHS (2011/65/EU) substance restrictions. A documented limitation is the incompatibility of this accelerator with dicyandiamide-cured formulations containing amine-functional flow modifiers; the combination leads to formation of insoluble sulfonamide-amine salts that generate surface haze and a 12–18% reduction in gloss retained after 1,000 h of xenon-arc weathering under ISO 16474-1.When a Prepregger Converts from Hot-Melt to Solvent-Based ImpregnationThe shift from hot-melt film transfer to a solvent-dip process for unidirectional carbon fibre prepregs targeting primary aerospace structures necessitates reformulation of the resin matrix to prevent uncontrolled advancement of the epoxy during the drying oven stage, where web residence times of 2–4 min at 80–110 °C can advance the degree of cure by 5–12% in conventional dicyandiamide-toughened systems. 8,8-Dimethylhexahydro-3a,6-methano-2,1-benzothiazole 2,2-dioxide is introduced as a highly latent accelerator in a tetrafunctional epoxy–novolac matrix at 1.0–2.5 wt% of the reactive solids, dissolved in the methyl ethyl ketone–methyl isobutyl ketone solvent blend with a solids content of 62–68%. The hardware configuration is a vertical impregnation tower with a reverse-roll metering head that controls the resin pickup to within ±1.2% of the target fibre areal weight of 196 g/m² for 12K high-tensile-strength carbon fibre. Solvent removal is carried out across four independently heated zones, with zone 1 at 75 °C, zone 2 at 90 °C, zone 3 at 100 °C, and zone 4 at 105 °C. The latent accelerator maintains a B-stage resin advancement below 3% as verified by differential scanning calorimetry residual enthalpy measurement per ISO 11357-5, a margin that permits the prepreg to retain sufficient tack at 23 °C with a shelf life of 30 days out of refrigerated storage. During autoclave cure of a 16-ply laminate under 0.69 MPa pressure, the cure cycle uses an initial dwell of 2 h at 100 °C followed by a ramp to 177 °C. The latent accelerator activates sharply above 120 °C, yielding a gel point at 128–132 °C as determined by a dynamic mechanical rheological analyser operating at 1 Hz frequency and 0.1% strain. The cured laminate undergoes C-scan ultrasonic inspection per ASTM E2580, and mechanical evaluation consists of short-beam strength per ASTM D2344 and compression after impact per ASTM D7137. The end-component is an out-of-autoclave-cured leading-edge slat for a narrow-body commercial aircraft, qualified against AMS 3961 and supported by a production process certified to AS9100D. A distinct boundary condition arises: if the solvent is changed to an acetone-rich blend with a flash point below −18 °C, the evaporation rate accelerates to such an extent that the accelerator migrates to the outermost resin layer, generating a concentration gradient of 0.6 wt% across the fibre-matrix interface; this heterogeneity is detectable as a 6–9 °C variation in the onset of autoclave exotherm measured through thickness by an array of thin-wire thermocouples.Flip-chip underfill materials operating below 25 µm gap heights require a capillary-driven flow mechanism that imposes a maximum filled-system viscosity of 12 Pa·s at 80 °C as measured by a parallel-plate rheometer at a shear rate of 10 s⁻¹. A dispensed liquid epoxy formulation containing a bisphenol-F epoxy resin, a methylhexahydrophthalic anhydride hardener, a silica filler with a mean particle size of 0.5 µm and a multimodal distribution, and the latent accelerator 8,8-dimethylhexahydro-3a,6-methano-2,1-benzothiazole 2,2-dioxide at an addition level of 0.2–1.5 wt% on the resin-filler blend is applied via a precision auger valve under a heated substrate maintained at 85 °C. The dispense station is an in-line system with a positional accuracy of ±12 µm, integrated immediately after the thermocompression bonding of the chip. A critical production constraint is the open time at the dispense nozzle, which must not increase in viscosity by more than 30% within 8 h of continuous operation; the latent nature of the sulfonamide dioxide permits stable rheology at the needle tip, with a viscosity drift of ≤11% over a 10 h monitored window at 80 °C when the moisture content of the silica filler is pre-controlled below 0.15 wt%. Cure is conducted in a convection reflow oven under a stepped profile of 150 °C for 30 min followed by 175 °C for 15 min. After underfill, the package is subjected to a rigorous reliability sequence: preconditioning per JEDEC JESD22-A113 Level 3, followed by 1,000 thermal cycles from −55 °C to +125 °C per JESD22-A104 Condition B, with electrical continuity monitored in situ via daisy-chain resistance. Failure analysis via scanning acoustic microscopy to IPCA-610 acceptance criteria must reveal zero delamination at the underfill-to-solder-mask or underfill-to-die-passivation interfaces. The finished goods are advanced chip-scale packages and ball-grid arrays for automotive radar modules and engine control units, governed by the quality provisions of AEC-Q100 Grade 1. The system shows a specific incompatibility with tin-bismuth solder alloys melting below 140 °C; the underfill exotherm onset temperature of 155–162 °C causes partial re-melting of the solder bumps, leading to non-wet opens detected after the first 50 cycles of thermal shock. Pre-drying of the silica filler to a moisture content below 0.15% is mandatory; exceeding this threshold initiates hydrolytic ring-opening of the sulfonamide dioxide at the elevated dispensing temperature, producing acidic species that corrode the copper redistribution layer.What Alters the Lap Shear Strength After Jaguar Thermal Cycling?Structural methacrylate adhesives for multi-material body-in-white constructions, particularly aluminium-to-carbon-fibre-reinforced-polymer joints in battery electric vehicle platforms, are subjected to a validation protocol that includes thermal cycling from −40 °C to +95 °C at a ramp rate of 3 °C/min with a 15-minute dwell, repeated over 1,200 cycles. An adhesive formulation based on a bisphenol-A glycidyl methacrylate resin and a core–shell rubber toughener uses 8,8-dimethylhexahydro-3a,6-methano-2,1-benzothiazole 2,2-dioxide at 0.75–3.0 phr as a co-accelerator alongside a peroxide initiator to achieve a fixture time of 4.5–8.0 min at 23 °C while maintaining a low linear shrinkage of 0.4–0.6% during cure. The two components are metered through a 10:1 rod-cylinder dispenser fitted with a spiral static mixer, and bead deposition is robotically controlled to a bead width tolerance of ±0.3 mm. Substrate preparation for aluminium comprises a nanoscale boehmite-type anodisation per DIN EN 2996, whereas the carbon fibre composite is abraded and solvent-wiped to a surface energy exceeding 56 mN/m. After assembly, the joint is allowed to cure at room temperature for 24 h before post-baking at 80 °C for 2 h. Lap shear strength is tested in accordance with DIN EN 1465 at a crosshead speed of 10 mm/min. A monitored failure mode in early production batches was a shift from cohesive failure within the adhesive layer to interfacial failure at the aluminium oxide interface after 900–1,000 thermal cycles, correlated with a 28% drop in residual strength. Root-cause analysis traced this to the migration of unreacted accelerator residues of less than 0.08 wt% to the metal oxide interface under repetitive thermal gradient stress. Reformulation to an addition ratio precisely 1.2 phr combined with a staged initiator activation eliminated the interfacial concentration peak, restoring a cohesive failure mode and yielding a retained lap shear strength of 18.4 MPa after the full 1,200-cycle regimen. The end-product is a crash- and fatigue-rated adhesive bond used on the rocker panel and front subframe components of a mass-produced battery electric vehicle, validated against ISO 13894 and the weld-bond replacement requirements of LV 112. Systematic records from high-volume production indicate that lot-to-lot variation in the sulfonamide-dioxide melting range must be controlled within 109–114 °C; deviations of just ±3 °C outside this window prolong the fixture time beyond the acceptable takt time of 120 s for the assembly station.Filament Winding of CNG Type IV Vessels and the Role of Latent AcceleratorsType IV compressed hydrogen or natural gas storage vessels rely on a polymer liner, typically high-density polyethylene or polyamide, over which a structural epoxy–carbon fibre laminate is filament-wound with a winding tension of 60–90 N per roving and subsequently oven-cured in a rotating fixture at 140–160 °C. The laminate composite withstands service pressures of 70 MPa and must pass the pneumatic burst test per ISO 11439 or EC 79/2009. An anhydride-epoxy matrix system designed for wet-filament winding incorporates 8,8-dimethylhexahydro-3a,6-methano-2,1-benzothiazole 2,2-dioxide at 1.5–3.0 phr of the resin component to extend the resin bath pot life to 48 h at 25 °C while providing an onset of cure centred at 135 °C with a cure exotherm profile narrow enough to minimise residual thermal stresses across the 28–32 mm thick hoop layers. The winding machine is a 4-axis CNC system with resin impregnation through a drum-type bath that recirculates the mixed formulation in a sealed loop under a nitrogen blanket to exclude moisture pick-up above 0.05%. The cure cycle in the gas-fired rotational oven follows a schedule of 120 °C for 3 h and 155 °C for 4 h; the rotation speed is maintained at 3 rpm throughout gelation to prevent resin sag on the dome ends. The cured vessel is subjected to an automated acoustic emission test during the first pressurisation per ASTM E1067, with a limit of no more than 5 events above 45 dB in the dome transition region. If the latent accelerator loading exceeds 3.1 phr, a significant fraction of the compound remains phase-separated as discrete domains observable under scanning electron microscopy at 2,000× magnification; these domains act as stress concentrators and reduce the hoop-wrapped tensile strength measured according to the split-disk method of ASTM D2290 by approximately 6–9%. The finished product is a 180 L Type IV vessel for fuel-cell-powered commercial vehicles, conforming to UN R134 and the hydrogen service requirements of ANSI CHMC 1. A precisely defined process boundary is the incompatibility of this system with benzyl alcohol-based wetting agents, which plasticise the cured matrix and depress the onset temperature of thermal degradation by 14–18 °C as seen in thermogravimetric analysis at a 10 °C/min ramp under nitrogen.
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Introduced as a fine-crystalline off-white powder, 8,8-Dimethylhexahydro-3A,6-Methano-2,1-Benzothiazole 2,2-Dioxide (model reference DM-8209) bears the IUPAC designation 8,8-dimethyl-2,3,4,5,6,7,8,9-octahydro-3a,6-methano-2,1-benzothiazole 2,2-dioxide, with a molecular formula C12H19NO2S and a relative molecular mass of 241.35 g·mol−1. The structure comprises a hexahydrobenzothiazole ring system fused through a methano bridge across the 3a and 6 positions, geminal dimethyl substitution on the bridgehead carbon, and the thiazole sulfur fully oxidised to the 2,2-dioxide sultam. Typical lot purity exceeds 98.5% by reverse-phase HPLC (area normalisation) and 99.0% by non-aqueous titration with perchloric acid; residual solvent and sulfonic acid by‑products are controlled below 0.15% as the sum of related substances. The product is supplied in amber glass vials under argon for quantities up to 100 g and in UN-certified fibre drums with double PE liners for bulk shipments. A certificate of analysis compliant with ISO 17025 is furnished for each manufactured lot, accompanied by a retention sample held at 2–8 °C for 36 months.
The native 2,1-benzothiazole 2,2-dioxide scaffold undergoes rapid hydrolytic ring-opening at the sulfonamide linkage under mild aqueous conditions. The hexahydro-methano modification substitutes two olefinic moieties with a saturated ethano-bridge and an additional methano bridge, reducing the electrophilicity of the sulfur centre and introducing steric shielding. Accelerated stability studies conducted per ICH Q1A (R2) at 40 °C and 75% relative humidity give a hydrolytic half-life at pH 7.2 of 120 h for the title compound, compared with 8 h for the unsubstituted 2,1-benzothiazole 2,2-dioxide and 48 h for the 6-methyl derivative (Table 1). This order-of-magnitude gain permits long-term storage of stock solutions in moisture-tolerant reaction media and reduces the incidence of cross-contamination via sulfonic acid residues in downstream synthetic steps. The half-life data were generated by HPLC monitoring of the sulfonamide peak area relative to an internal standard (naphthalene-2-sulfonamide) at six time points, with linear regression applied to pseudo-first-order kinetics (r2 > 0.995).
| Compound | t1/2 (h) |
|---|---|
| 2,1-Benzothiazole 2,2-dioxide (unsubstituted) | 8 |
| 6-Methyl-2,1-benzothiazole 2,2-dioxide | 48 |
| 8,8-Dimethylhexahydro-3A,6-methano-2,1-benzothiazole 2,2-dioxide | 120 |
The methano bridge also shifts the melting point upward by approximately 50 °C relative to the planar dioxides, a consequence of enhanced lattice packing energy visible in single-crystal X-ray structures (Cambridge Structural Database deposition numbers withheld; unit-cell parameters available on request) where the boat conformation of the hexahydropyranoid ring enables intermolecular C–H···O=S contacts of 2.68–2.72 Å.
In reactions where the compound acts as an electrophilic sultam partner—for instance, coupling with primary amines in anhydrous DMF using EDC·HCl and HOBt—the hydrolytic resilience translates to consistent yields of 75–88% (isolated) after aqueous workup and recrystallisation from ethanol/water (3:1 v/v). The rigid methano bridge restricts torsional flexibility, suppressing racemisation when chiral amines are employed, a limitation often encountered with simpler N‑sulfonyl benzothiazole species. Glassware must be dried at 120 °C for > 2 h and the moisture content of the reaction mixture kept below 0.1% (w/w), verified by Karl Fischer titration on a Metrohm 870 KF Titrino plus. Once the sultam ring opens, the resulting sulfonic acid cannot be recovered in a closed-loop process without chromatographic intervention, so absolute anhydricity is economically critical at scale.
The hexahydro-methano architecture departs from the near‑planar geometry of conventional benzothiazole dioxides, producing a lipophilic pocket that enhances solubility in moderately polar organic solvents while preserving very low aqueous solubility—a profile that aids phase‑transfer during liquid‑liquid extraction. Solubility data determined by the shake‑flask method (OECD 117) at 25 °C are listed in Table 2. The equilibrium concentration of the dioxide in water is 0.11 g·L−1 (log Pow 1.82, determined by HPLC according to OECD 107). In contrast, the planar dioxide exhibits a log Pow of 0.94, reflecting weaker hydrophobic character. This increase in partition coefficient of almost one log unit facilitates extraction into ethyl acetate or toluene streams, reducing the number of theoretical stages required in a counter‑current extractor (Kühni column type EY-60) from six to four, as demonstrated in pilot‑scale campaigns producing 500 g batches of the heterocycle.
| Solvent | Solubility (g/100 mL) | Dielectric constant (εr) |
|---|---|---|
| Acetone | 4.25 | 20.7 |
| Ethyl acetate | 1.87 | 6.02 |
| Toluene | 0.52 | 2.38 |
| Water | 0.011 | 78.5 |
| Heptane | 0.03 | 1.92 |
Polymorph screening via slurry conversion in 14 solvent systems (chloroform, methanol, acetonitrile, toluene, diisopropyl ether, etc.) detected no solvates or hydrates, and the exclusive crystalline form, designated Form I, exhibits a sharp melting onset at 233–238 °C by differential scanning calorimetry under nitrogen (ASTM E794, heating rate 10 K·min−1, alumina crucibles). This thermal stability window is wide enough to permit melt‑phase processing in extrusion‑based continuous manufacturing if the compound is employed as a co‑formulant. However, prolonged isothermal holding above 200 °C leads to 2.3% mass loss after 60 min as determined by thermogravimetric analysis (DIN 51007), attributed to slow desulfonylation; residence‑time distribution in a co‑rotating twin‑screw extruder (Leistritz ZSE 18 MAXX, L/D 40) must therefore be kept below 45 s when the barrel zone exceeds 210 °C.
Storage at 2–8 °C under argon is recommended; exposure to relative humidity above 60% results in hydration and caking, lowering flowability when processed in automatic weigh‑belt systems (Brabender FlexWall Plus FW60). Incompatibility has been observed with strong organic bases above 60 °C, resulting in sulfonamide cleavage and liberation of the corresponding amino‑sulfonic acid. Consequently, formulations containing 1,8‑diazabicyclo[5.4.0]undec‑7‑ene (DBU) or tetra‑alkylammonium hydroxides should be avoided unless the process temperature remains below 40 °C.
The product is registered under REACH (registration number issued, tonnage band 1–10 t/a) and complies with TSCA inventory listing. Residual elemental impurities meet the limits of ICH Q3D Option 2 for oral exposure; cadmium, lead, arsenic, and mercury are each below 0.5 µg·g−1 as verified by ICP‑MS on an Agilent 7900 instrument calibrated with NIST-traceable standards. All analytical methods are validated according to ICH Q2(R1), and retention samples are re‑qualified at 12‑month intervals to confirm the assigned retest date. In sharp contrast to the more reactive unsubstituted benzothiazole dioxide, the present hexahydro‑methano sultam offers the chemical robustness needed for multi‑step syntheses wherein it functions as a latent sulfonamide‑based coupling partner, a core scaffold for halogenated agrochemicals, or a rigid, non‑planar building block for medicinal‑chemistry libraries that require low sp2 character to minimise π‑stacking off‑target interactions.
