Reactions of thioketones with dichlorocarbene

The reactions of sterically crowded cycloalkanethiones of type 2 with CHCl3 /NaOH under phase-transfer catalysis (PTC) with benzyl(triethyl)ammonium ch loride (TEBA) as catalyst afforded the corresponding 'gem.-dichlorothiirane s' of type 3 in good yields (cf. Scheme 2 and Table). The desulfurization, which, in some cases, occurred spontaneously, led to (dichloromethylidene)c ycloalkanes of type 4. Similar results were obtained using Seyferth's reage nt in boiling benzene. In the case of 2,2,6,6-tetramethylcyclohexanethione, reaction under PTC conditions after 3 h yielded only the corresponding dic hloromethylidene derivative: on the other hand, workup after 1 h gave (2,2, 6,6-tetramethylcyclohexylidene)methanethione (thioketene 9; Scheme 5).