1.3- Dithiole-2-thiones acetylene derivatives

More recently, a new method was developed (05MI3) for photochromic 4,5-dithienyl(dibenzothienyl)-l,3-dithiol-2-ones 229 and dithiol-2-thiones 230 from acetylene derivative 228 (Scheme 66). Compounds 230 are good building blocks for the design of photochromic fluorophores. 

The cycloaddition reaction between l,2-dithiole-3-thiones that are not substituted in the 5-position and acetylene derivatives has been found to give the thioaldehydes (4) as brown solids or pastes. " The products could not be obtained analytically pure, but were characterized spectroscopically. The yields of the thioaldehydes were rather dependent on the... 

The thiones (28) show some interesting similarities in behaviour to their simpler analogues, the l,2-dithiole-3-thiones. Thus, methylation converts them into salts (31), and cycloaddition reactions with acetylenes yield 1,3-dithiole derivatives (32), analogous to the isothiathiophthens (33), the formation of which, from l,2-dithiole-3-thiones, is discussed in a recent paper, elaborating an earlier report (see also Chapter 10, p. 532). 

AU ethioIates and Selenolates. Sodium alkynethiolates are generated from 1,2,3-thiadiazoles (16) and reacted with CS2. Nucleophilic attack of sodium alkynethiolates to CS2 followed by the intramolecular cyclization proceeded to give 1,3-dithiole-2-thiones (17) in 57-98% yields (eq 2)P Lithium alkynethiolates, which are derived from terminal acetylenes, BuLi, TMEDA, and elemental sulfur, can also be used in this cyclization reaction (eq 13). In the case of the lithium salts, CS2 is added at —90 °C, and the reaction mixture is quenched by adding water containing THF at this temperature to lead to (17). Lithium alkyneselenolates participate in this type of transformation (eq 14). The reaction mixture is quenched with alkyl thiocyanates or a combination of elemental selenium and alkyl iodides to give 1,3-selenothiole-2-thiones (18) in 80-98% yields. The reaction is quenched in a similar manner to that from the lithium alkynethiolates. ... 

In a study of the oxidation of various heterocyclic thiones with peroxyacetic acid, l,2-dithiole-3-thiones (10) carrying electron-withdrawing substituents have been found to give l,2-dithiole-3-ones rather than dithiolium salts. Experimental details have been published for addition reactions of l,2-dithiole-3-thiones with acetylenes, and with benzyne. Reactions with enamines, leading to thiopyran derivatives (11), have been described. ... 

Acetylenic starting materials have also been used in the preparation of a series of amidine derivatives of l,3-dithiole-2-thione and some related compounds, and in the synthesis of l,3-dithiole-4-carboxylic acids. ... 

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