Dichlorocyclobutenones previously obtained only with difficulty were prepared by the cycloaddition of dichloroketene with alkynes in the presence of phosphorus oxychloride in fair to good yields. The regiochemistry of addition can be rationalized on the basis of electronic factors except in the case of (trimethylsily1) acetylenes which exhibit unusual regioselectivity. Thermolysis of the cyclobutenones in the presence of alcohol led to ...
