Reactions of 2-Mercaptobenzothiazoles

Reactions of 2-Mercaptobenzothiazoles. The (un)substituted 2-mercapto-benzothiazoles react with an amine and O2 in the presence of HjO and cobalt phthalocyanine to give high yields of sulphenamide (213) they also react with morpholine in the presence of NaOCl. These sulphenamides could be the first step in the conversion into disulphides (214). The 2-mercaptobenzothiazoles are substituted in alkaline solution with halo-compounds. ... 

Reactions of 2-mercaptobenzothiazoles. 2-Mercaptobenzothiazole salt reacts with nitrohalobenzenes to form substitution products (198 ) >250 Similar results are obtained with chloroalkyl-... 

Reactions of 2-aminobenzothiazoles 179 Reactions of 2-mercaptobenzothiazoles 180 Reactions of benzothiazole-2-acetonitriles 180 Other reactions of benzothiazoles 181 Benzisothiazolines and Benzothiazolin-2-ones 182 Synthesis 182 Reactions 182... 

Torii S, Tanaka H, Ukida M (1978) Electrosynthesis of hetero-hetero atom bonds 2. An efficient preparation of (2-benzothiazolyl)- and thiocarbamoyl-sulfenamides by electrolytic cross-coupling reaction of 2-mercaptobenzothiazole, bis(2-benzothiazolyl) disulfide, and/or bis(dialkylthiocarbamoyl) disulfides with various amines. J Org Chem 43 3223-3227... 

The biocidal activity of the thiadiazine (12) is probably related to the production of methyl isocyanate inside the cell by hydrolysis (equation 7). Isocyanates are known to have fungicidal properties (B-69MH1502), thought to be due to their reaction with sulfhydryl groups to form dithiocarbamates. The formation of these last mentioned compounds, by ring cleavage, might also explain the activity of 2-mercaptobenzothiazole (16). 

In the case of sulfenamide accelerators, the inhibitor appears to function by reacting with 2-mercaptobenzothiazole (77MI11506) so suppressing the catalytic pathway (equation 11). This is illustrated by the reaction between 2-mercaptobenzothiazole and IV-cyclo-hexylthiophthalimide (39), one of the most effective PVIs currently in use (equation 12) (73MI11500). It is likely that the reaction between the PVI and amines (equation 13) also makes a contribution to the mechanism of inhibition (77MI11506). 

Scheme 13.13 Reaction pathways of 2-mercaptobenzothiazole in the presence of Raney Ni in refluxing methanol.

Aminopenicillanic acid (8) was converted to 6(5)-bromopenicillanic acid by trapping of the diazo-intermediate with hydrogen bromide. Esterification of the dicyclohexylamine salt (93) with p-methoxybenzyl bromide, followed by oxidation, afforded the sulphoxide (94) in 60% yield from 6-APA. Elaboration of this sulphoxide to the disulphide (96) was effected by the procedure established by Kamiya et al. [98] the sulphenic acid (95), formed by heating the sulphoxide to reflux in toluene, was intercepted by reaction with 2-mercaptobenzothiazole to yield the disulphide (96). The latter was transformed by base-catalysed double bond isomerization to the conjugated ester disulphide (97) [95% yield from (94)]. Reductive formylation of disulphide (97) then provided the formylthio-derivative (98). Cyclization of the oxalimide (99), obtained by ozonolysis of... 

Electrochemical oxidation of 2-mercaptobenzothiazole proceeds via the radical 213 which dimerizes to the corresponding disulfide this electrochemical reaction is of synthetic value in preparing the disulfide. ... 

A convenient synthesis of 2-mercaptobenzothiazoles 44 features an exclusive ortho-selective nucleophilic aromatic substitution reaction of or//zo-haloanilines 41 and subsequent intramolecular cyclization of the intermediate O-ethyl carbonodithioates 43 <05JHC727>. 2-Mercaptobenzothiazoles 44 are readily converted to the corresponding 2-chlorobenzothiazoles 45 upon treatment with sulfuryl chloride. 

Thus, one theory for delayed action is the quenching of free radical crosslink precursors by monomeric polysulfides. It has been found that, if bisalkylpolysullides are mixed with uncured rubber stocks, more delay results. It is also been shown that the early reaction products formed by the interaction between accelerator and sulfur (Ac-S -Ac) are inhibitors of crosslink formation. The very substances that give rise to the formation of the crosslink precursor (rubber-Sjc-Ac) inhibit the formation of the crosslinks. We note that other mechanisms for delayed action have been proposed. In the case of acceleration by benzothiazolesulfenamides, the accelerator is depleted in an autocatalytic fashion with the formation of 2-mercaptobenzothiazole (MET). The rate of this depletion is about proportional to the amount of MET present. There is strong evidence, which indicates that the following reactions occur in sulfenamide-accelerated systems ... 

Organic chemical accelerators were not used until 1906 (65 years after the Goodyear-Hancock development of unaccelerated vulcanization [Fig. 8]), when the effect of aniline on sulfur vulcanization was discovered by Oenslager [11]. This could have been, at least partially, in response to the development of pneumatic tires and automobiles near the turn of the century. Aniline, however, is too toxic for use in rubber products. Its less toxic reaction product with carbon disulfide, thiocarbanilide, was introduced as an accelerator in 1907. Further developments lead to guanidine accelerators [12]. Reaction products formed between carbon disulfide and aliphatic amines (dithiocarba-mates) were first used as accelerators in 1919 [13]. These were and are still the most active accelerators with respect to both crosslinking rate and extent of crosslink formation. However, most of the dithiocarbamate accelerators give little or no scorch resistance and their use is impossible in many factoryprocessing situations. The first delayed-action accelerators were introduced in 1925 with the development of 2-mercaptobenzothiazole (MET) and 2-... 

Scheme 19.40 Mercaptobenzothiazoles and benzoxazoles in Ugi-Smiles couplings. Scheme 19.41 Passerini-Smiles reaction of 2-nitrophenol.

Other mechanisms for delayed action have been proposed. In the case of acceleration by benzothiazolesulfenamides, the accelerator is depleted in an autocatal)4ic fashion with the formation of 2-mercaptobenzothiazole (MET). The rate of this depletion is about proportional to the amount of MET present. There is strong evidence that indicates that reactions occur in sulfenamide-accelerated systems as shown in Scheme 5. 

The heterocyclic N,S compounds Dazomet (Section 3.3.16) and Taurolin (Section 3.5.2.) can be regarded as formaldehyde releasing compounds therefore they are listed in Section 3. The A -hydroxymethyl derivative of 2-mercaptobenzothiazole (Section 3.4.10.2) is a formaldehyde releasing compound too and is described under Section 3.4, Reaction products of amides and formaldehydes . 

Hilton and Altenau and Hayes and Altenau used mass spectrometry to qualitatively identify volatile antioxidants in sheet samples of synthetic styrene-butadiene rubbers and rubber type vulcanizates. They extracted the polymer with acetone in a Sohxlet apparatus, removed excess solvent and dissolved the residue in benzene. Substances identified and determined by this procedure include N-phenyl-fi-napthylamine, 6-dodecyl-2,2,4-trimethyl 1,2-dihydroquinolines, trisnonyl-phenyl-phosphite, isobutylene - bisphenol A reaction product, 2-mercaptobenzothiazole sulphen-amide (accelerator) N-cyclohexyl-2-benzothiazole sulphenamide, N-tert-butyl-2-benzo-thiazole sulphenamide, 2-(4-morpolinothio) benzothiazole, 2-(2,6-dimethyl-morphal-inothio) benzothiazole, N,N -diisopropyl 2-benzothiazoles, 2-mercaptobenzo-thiazole and N,N -dicyclohexyl-2-benzothiazole sulphamide. 

The electrochemical behaviour of pre-treatments obtained with direct addition of inhibitor in sol-gel solution (morphology shown in Fig. 14.7A) is similar or even worse than that for the undoped system. It is likely that the addition of 2-mercaptobenzothiazole to the sol-gel solution negatively affects hydrolysis and condensation reactions involved in the deposition of the sol-gel layer, affecting film continuity. This might be reflected in the electrochemical behaviour. 

The behavior of the 2-mercapto-4-arylthiazoles in this reaction would seem to be analogous to that of the 2-mercaptobenzothiazoles (137). It appears that monosulfide compound (195) cannot be obtained from 2-chloro- and 2-mercapto-4-phenylthiazoles (given the difficulty of preparing it in this way) but rather by the action of the 2-mercapto-4-phenyl-thiazole on the intermediary, 4-phenyl-2-isothiazolyl isothiouronium chloride (194), as in Scheme 101. 

Properties of zinc salts of inorganic and organic salts are Hsted in Table 1 with other commercially important zinc chemicals. In the dithiocarbamates, 2-mercaptobenzothiazole, and formaldehyde sulfoxylate, zinc is covalendy bound to sulfur. In compounds such as the oxide, borate, and sihcate, the covalent bonds with oxygen are very stable. Zinc—carbon bonds occur in diorganozinc compounds, eg, diethjizinc [557-20-0]. Such compounds were much used in organic synthesis prior to the development of the more convenient Grignard route (see Grignard reactions). 

Very weak acids such as 2-mercaptobenzothiazole (32) [27], saccharine (34), 5,5-diphenylthiohydantoin (36) [31], or 5-yhdene-thiohydantoins (38) [32] form salts with methylamine gas (Scheme 4). Such quantitatively formed salts (33,35,37,39) cannot be obtained in solution. This new possibility of reaction was studied and interpreted with AFM [1,27]. Even C-H acids such as barbituric acids 40, which crystallize as the triketo tautomers, form the ammonium barbiturates 41 with gaseous bases such as ammonia or dimethylamine with great ease [32]. 

The thiol group can also be found in heterocyclic compounds such as 2-mercaptobenzothiazole (9) and echinoclathrine C (10). Compound 9 was isolated from the symbiont bacterium Micrococcus sp., which was obtained from the sponge Tedania ignis [13]. The pyridine alkaloid echinoclathrine C (10) and its S-acetylated derivative, echinoclathrine B (11), were isolated from the Okinawan sponge Echinoclathria sp. [14]. The position of the hydroxyl and acylamino group on the phenyl ring in echinoclathrines (11 and 10) was recently corrected [15]. Compound 11 showed weak immunosuppressive activity in the mixed lymphocyte reaction assay with an IC50 of 9.7 pg/ml [14]. 

---