The thiocarbonyl ylides 13 and 1, 3-thiazol-5 (4H)-thiones 1 undergo a smooth reaction to yield spirocyclic 1, 3-dithioIanes 14-16 (Schemes 4 4). The 1, 3-dipolar cycloadditions occur in a regioselective manner, but the orientation of the thiobenzophenone-S-methylide (13b) differs from that of the cycloalkane thione-S-methylides 13a and 13c. Whereas the 1, 3- cycloadduct with 13b is formed in accordance with frontier-orbital considerations, the ...
![4,4-dimethyl-2,9,9-triphenyl-1,6,8-trithia-3-azaspiro[4.4]non-2-ene Structure](https://image.chemsrc.com/caspic/331/138197-19-0.png)