1.2- Dithietes synthesis

Tire first synthesis of 3,4-di-ferf-butyl-l,2-dithiete (172) was performed by treatment of 173 with Lawesson s reagent (LR). Direct thionation of the diketone 174 failed to yield 172 [82JCR(S)314]. 

The synthesis of 1,2-dithietes was extensively described by Zoller in CHEC-II(1996) <19%GHEC-II(1B)1113>, and the literature until 1995 was summarized. Since that time, a few interesting procedures have been reported. The oxidation of the titanium complex 224 with sulfuryl chloride in benzene gave 3,4-dimethoxycarbonyl-l,2-dithiete 225 in 66% yield. Macrocyclic compounds 226 and 227 were isolated as by-products (Equation 46) <1998JOC8192, 1999PS431>. 

The synthesis of the stable 1,2,3-trithiole (120) has been reported by Tokitoh et al. <89TL2955>. The authors have photolyzed (120) in an argon matrix at low temperature while following changes in the electronic spectrum. This experiment revealed that two intermediates are formed, namely the 1,2-dithiete (121) and the thione (122). These intermediates are seen as forming from initial formation of thiosulfoxide (123) which is further transformed to the spirodithiirane (124) which serves as precursor to (121) and (122). 

The synthesis of dithiins may proceed via 1,2-dithiete intermediates. In these cases, yields of dithiins are usually low but the chemistry is interesting <93BCJ623>. 

Dithiolene synthesis according to (i) was the first entry to the class of tris-dithiolenes King reacted the dithiete (12) with Mo(CO)6 to obtain Mo(tfd)3. The reduction of the julolidinedithione by NaBH4 in THF MeOH, followed by acidification and reaction with aqueous NiClj, led to (9) in excellent yield. As is evident from the MO diagram of dithiolenes (see Section 16.5.3,7) and their established redox properties, method (iii) applies only to dithiolenes with strongly electron-donating substituents, which may stabilize the cationic intermediates. 

Choi KS, Akiyamal, HoshinoM, Nakayama J (1993) A convenient synthesis of 1,2-dithietes and 1,2-dithioxo compounds stabilized by buttressing and resonrmce effects, respectively, by sulfuration of alkynes and elemental sulfur. Bull Chem Soc Jpn 66 623-629... 

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