Type E Syntheses

Type E (N—C—C—S 4- O Syntheses.—Successive esterification of L-cysteine hydrochloride and treatment of the product (63) with compound (64) yields the A -thiazoline (65) (see later).  

Type E (N—C—C—S + C) Syntheses.—2-Acyl-A -thiazolines (99) are accessible by the adaptation of known reactions,by the condensation of cysteamine (94 R = = H) and 2,2-dialkoxyalkanenitrile, followed by 

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In another variation of a type E synthesis, thioamides or thioureas condense with /V,/V-dimcthylacylamide dimethyl acetal to give imino compounds which react with amino-transfer reagents like hydroxylamine-O-sulfonic acid and mesitylsulfonyloxyamine (MSH) to give 3,5-substituted-l,2,4-thiadiazoles in excellent yields <1996CHEC-II(4)307>. There have been no new reports of type E syntheses since the publication of CHEC-II(1996). 

A few examples previously assigned to this class on the basis of postulated intermediates have been reassigned to type E syntheses (75BCJ310, 73CL917). At the present time there are no authenticated examples of this type of ring closure. 

Type E Syntheses of A -Thiazolines (N-C-C-S + C). PhCOjH reacts with NH2(CH2)2SH in the presence of Ph3P, CCI4, and tertiary bases to give 45% of A -thiazoline (122). In addition, we mention the synthesis of the nitro-sothiazoline (123). ... 

Type E Syntheses (C Hs-N + C-S). Treatment of substituted anilines with NH4SCN gives substituted 2-aminothiazoles and there are also references concerning the synthesis of benzothiazoles. 

Type E Syntheses N—C — C—S + C). The reaction between ketones RCOCH2R (R = pentyl, hexyl, etc.), ethyleneimine, and sulphur gives a mixture of 2,2-dialkylated thiazolidines and 5,6-dihydrothiazines, but only the former products are obtained when HSCH2CH2NH2 is used. A combination of the azirines (79 R = H R = H or alkyl) or (79 R R = Me), 2-hydroxy- or 2-dimethyIamino-tetrahydropyran, and hydrogen sulphide produces 2-(4-hy-droxybutyl)-thiazolidines (80). ... 

Type E Syntheses [CNCS + N].— The interaction of thiobenzoyl isocyanate and nitrosobenzene yields, surprisingly, the l,2,4-thiadiazolin-3-ones (79) (58%), with elimination of oxygen, the fate of which is as yet not elucidated. The formulation of the products is confirmed by their unequivocal synthesis by the oxidative cyclization of (80). ... 

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