Reaction of dichloroketene and sulfenc with N,N ‐disubstituted 2‐aminomethylene‐1 ‐indanones. Synthesis of indeno[ 1,2‐b ] pyran and lndeno[2,l‐e] ‐1,2‐oxathiin derivatives

The 1,4‐cycloaddition of dichloroketene to N,N ‐disubstituted 2‐aminomethylcnc‐l‐indanones afforded N,N ‐disubstituted 4‐ainino‐3,3‐dichloro‐3,4‐dihydro‐2‐oxoindeno[1,2‐b ]pyrans only in the case of full or partial aromatic N‐substitution. The diphenylamino adduct gave 3‐chloro‐4‐diphenylamino‐2‐oxoindeno[ 1,2‐b]pyran by dehydrochlorination with DBN. The 1,4‐cycloaddition with sulfene occurred only in the case of 2‐diethylaininomethylene‐1‐indanone to give 4‐diethylamino‐3,4‐dihydroindeno[2, 1‐e]‐1,2‐oxathiin 2,2‐dioxide, a derivative of a new hetero‐cyclic system.