Tetracyanoethylene oxide TCNEO

The stable dicyanomethylides 274, made directly from the triazolopyridines and tetracyanoethylene oxide (TCNEO) reacts more slowly with MEP in acetonitrile to give mainly indolizines, with cyclazines as secondary products formed... 

Tetracyanoethylene oxide (TCNEO) not only oxidizes sulfides to sulfoxides but also reduces sulfoxides to sulfides with generation of two molecules of carbonyl cyanide (17). The reduction mechanism involves a zwitterion intermediate (15) that produces sulfide and two molecules of (17) by simultaneous cleavage of the C—C and O—S bonds. A mechanism (Scheme 14) that involves a zwitterion (16) as a common intermediate is proposed for the formation of ylide and sulfoxide.311... 

Triazines react with tetracyanoethylene oxide (TCNEO) to afford the stable triazinium 2-dicyanomethylides 84. 

The synthesis of pyrrolonaphthyridine derivatives has been reported from 1,3-dipolar cycloaddition reaction of naphthyridinium dicyanomethylides with DMAD. Starting from [1,5]- and [1,8]-naphthyridines (139), dicyanomethylides (140) were prepared on treatment with tetracyanoethylene oxide (TCNEO) in THE and they underwent 1,3-cycloaddition with DMAD in acetonitrile to afford aromatic products (142) after elimination of HCN from the adducts (141) (Scheme 18). Pyrrolo[2,l-/]naphthyridine (143) was obtained when the N-6 dieyanomethylide of [l,6]-naphthyridinium was employed <93H(36)1945>. 

Tetracyanoethylene (TCNE) or its oxide (TCNEO) reacted with thione 41 to give the dicyanomethylene product 42 (Scheme 22) <1997J(P1)3345>. This product can be obtained also from the same thione 41 and dihalogenated malononitriles <2002J(P1)1236> in higher yields. 

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