Addition de l'acide thiocyanique aux acétyléniques à l'aide de Hg(II). II: obtention d'isothiocyanates vinyliques par mercuration-protodemercuration

Abstract Thiocyanic acid HSCN is added to some acetylenic compounds R 1 -C& 2 through a two-step one-pot procedure wich involves, first, the generation in CH 2 Cl 2 of β-thiocyanato and/or β-isothiocyanato alkenyl mercuric coupounds R 1 -C (SCN)=CR 2 -Hg- by addition of mercury (II) thiocyanate Hg(SCN) 2 to R 1 -C& 2 then the substitution of mercury by hydrogen through acidic treatment. In proper conditions of stoechiometry and reaction time the process is tharmodynamically controlled and thus allows to obtain vinyl isothiocyanates R 1 -C(-NCS)CHR 2 even when the isomeric vinyl thiocyanates are kinetically favoured. Preparation of 3,3- dimethyl 2-isothiocyanato 1-thiocyanato 1-butene is also reported.