Thiazoles Dithiazoles

Li and co-workers introduced a rapid and efficient microwave-assisted method to prepare new disubstituted 1,3,4-thiazoles from 1,4-disubtituted thiosemicarbazides with the objective to obtain biologically active molecules. The intermediate l-aryloxyacetyl-4-(4-methoxybenzoyl)thiosemicarbazide was irradiated in an excess of glacial acetic acid in a domestic microwave oven and led to the formation of 2-(methoxybenzoyl-5-aryloxymethyl)-l,3,4-dithiazoles in good yields [30] (Scheme 20). 

Frere, S., Thiery, V. and Besson T., Eco-friendly microwave-assisted scaleable synthesis of 2-cyanobenzo-thiazoles via N arylimino 1,2,3 dithiazoles, Synth. Commun., 2003, 33, 3789-3798. 

Phosphonium ylides 66 attack 1,2,4-dithiazole derivatives 65 (Y = 0, S) mainly at the S-S bond to give intermediates 67, which can either afford thiazoline derivatives 68 or react further, with a second ylide molecule 66 at the C=Y bond, to finally yield new thiazole and dithiole derivatives 69 and 70. Compounds 70 are predominant in this mixture (yields > 50%). They are oxidized into known dithiole derivatives 71 (Scheme 8) <1993MI33, 1994PS105, 1995PS63, 1999PS393>. 

FVP at 600°C of l,3-thiazole-5(4//)-thiones 256 yields as main products the dithiazole derivatives 257 and as minor by-products the thiazete 258 and the disulfide derivatives 259 (Equation 5). A biradical intermediate has been suggested for the formation of azonylene 257 as well as for the other by-products <1998PJC1915>. 

In the complex of /ra r-2,2 -(l,4-but-2-enediyldithio)dithiazole (L) and silver nitrate, there is a symmetric center located at the midpoint of the l,4-but-2-enediyl group with the two thiazole rings antiparallel to each other <2005JST(752)40>. 

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