EFFICIENT ONE-POT SYNTHESIS OF DITHIENO(DIBENZOTHIENO)-FUSED CYCLOHEPTANONES, TROPONES, AND CYCLOOCTANONES

The reactions of alpha,beta-unsaturated amide/triflic anhydride comple xes (generated in situ from the corresponding amides and triflic anhyd ride) with dithiophenes and dithienylmethanes proceed as tandem alkyla tion-Vilsmeier-Haack acylation to form dithieno- and dibenzothieno-fus ed cycloheptanones and cyclooctanones in moderate to good yields. The reactions of 2-bromo-N,N-dimethylacrylamide/triflic anhydride complex allow preparation of tropones in a simple one-pot procedure. The react ion of 2,2-dibenzothienylmethane with dimethylacrylamide/triflic anhyd ride complex proceeds unusually to afford dimethylaminonaphthalene in addition to the predictable fused cyclooctanone.