1.3- Thiazol-5- -thiones, reaction with

The reaction of 2,5-dimethylisoxazoline-3-thione with 48% HBr produced, among other products, an isothiazole-3-thione, diisoxazole disulfide and 2,5-dimethylisoxazolin-3-one. In contrast, the reaction of 2-methyl-5-phenylisoxazoline-3-thione produced primarily disulfide 80CPB487). The reaction with H2S in 48% HBr produced an isothiazole-3-thione and a cyclic thiazole (Scheme 75) (80CPB487). 

The chemistry outlined in Schemes 8.32 and 8.34 illustrates the complexity of reactions that occur between thiocarbonyl compounds and diazo compounds. Heimgartner and co-workers (214-217) observed a similar reactivity pattern when they combined l,3-thiazol-5(477)-thiones (153) with diazoalkanes. When ethyl diazoacetate was used, additional reaction pathways occurred giving rise to a complex mixture of products (218). An interesting aspect of this chemistry involves... 

Methyl iodide, reactions with dialkyl-amino-thiazoles, 32. See also Alkylation 4-Methylthiazole, preparation of, from Na/NH3 reduction of 4-methyl-A-4-thiazoline-2-thione, 397 2-Methylthio-3-methylthiazolium salts, as catalyst for methylthiothiazole rearrangement, 406 Methylvinylketone, reaction of, with... 

Imidazoline-2-thiones and imidazolidine-2-thiones react with 1,2-dibromoethane in the presence of aqueous sodium hydroxide and a charge transfer catalyst (CTC), or with a-cyanobenzyl benzenesulfonate, to give the corresponding imidazo[3,l-f>]thiazoles (equation 10) (80JHC393, 61JOC2715). In an analogous reaction, the condensation of 5,5-diphenyl-2-thiohydantoin with ethylene dibromide yielded two isomeric products, (99 major) and (100 minor) (8lJCS(P2)789). 

Synthesis of this system, as depicted in Scheme 1, has been reported by Russian scientists (86KGS1690). Reaction of 5-n-propylpyrrolinyl-2-thione (5) with chloroacetic acid in benzene gives 7 in 50% yield. The reaction proceeds via the intermediate acid 6, which undergoes cyclization to furnish the bicyclic compound 7. The facile acid-catalyzed ring closure of thiazole is demonstrated by the fact that when 5 is heated with chloroacetic acid in the presence of sodium methoxide, the acid 10 is the only isolable product, which on treatment with hydrogen chloride affords 7. The bicyclic compound 7 reacts with p-dimethylaminobenzaldehyde in the presence of piperidine to yield 5,6-dihydro-2-p-dimethylaminobenzylidene-5-M-propylpyrrolo[2,l-/7]thiazol-3(2//)-one (9), presumably via 8. 

Synthesis of thiazolo[3,2-a]pyridin-3(2//)-one can also be accomplished by an alternate route in which a thiazole ring is built onto a pyridine ring. Thus, copper-catalyzed reaction of piperidine-2-thione (95) with methyl diazoacetate affords 5,6-dihydro-7//-thiazolo[3,2-a]pyridin-3(2//)-one 97) (80LAI68) (Scheme 22). During the reaction uncyclized intermediate (96) could not be isolated, it evidently cyclized immediately to the bicyclic product (97), whereas with the pyrrolidine-2-thione the corresponding uncyclized product was isolated (80LAI68) (Scheme 22). 

Disubstituted l,3-thiazol-5(4H)-thiones undergo cyclosubstitution reactions with acetylene carboxylates or acetylene carbonitriles to yield l,4Hlithiafulvenes <86HCA419>. 

The reaction of l,3-thiazole-5-(4 -thiones (191) with alkyl oxiranes in the presence of catalytic boron trifluoride etherate gives rise exclusively to spiroderivatives (192) in good yields (Scheme 45) <90HCA2287>. 

The thiazole ring of the 5-(D-arahfno-tetritol-l-yl)-imidazo[2,l-6]thiazol-ium olate 160 was assembled onto the imidazole ring of 4-(tetra-0-acetyl-D-flrabino-tetritol-l-yl)imidazoline-2-thione (156) by reaction with 2-bromophenylacetic acid (91MI7) (Scheme 47). 

Heimgartner s group investigated also the analogous thiirane formation of l,3-thiazole-5(4i /)-thiones 6.41 with phenyldieizomethane (Petit et al., 1994) and found the diastereoisomeric trans- and cw-thiiranes 6.47 and 6.48, respectively. They can be desulfurized stereospecifically with triphenylphoshine to the E)- and (Z)-benzylidene derivatives 6.49 and 6.50, respectively. Reaction of the same thiazole — thiones 6.41 with ethyl diazoacetate gives, however, a complex mixture of seven products (Kagi et al., 1994). 

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