Ring‐opening reactions of 3‐substituted 1‐azabicyclo[1.1.0]butane with dichlorocarbene

Reaction of 3‐ethyl‐1‐azabicyclo[1.1.0]butane ( 1a ) with chloroform‐potassium tert ‐butoxide afforded a ring‐opened product, 1,1‐dichloro‐2‐aza‐4‐ethylpenta‐1,4‐diene ( 4a ), which was characterized via conversion to the corresponding N ‐substituted 5‐chloro‐1,2,3,4‐tetrazole, Sa . Reaction of 3‐phenyl‐1‐azabicyclo‐[1.1.0]butane ( 1b ) with “Seyferth's reagent” (PhHgCCl 2 Br) afforded 1,1‐dichloro‐2‐aza‐4‐phenylpenta‐1,4‐diene ( 4b ), which also was characterized via conversion to a tetrazole derivative, i.e., 5b . Finally, the reaction of 1b with dichlorocarbene generated under phase transfer conditions (chloroform‐sodium hydroxide‐TEBA) was studied. At short reaction times (0.5 hour), the major reaction product was 4b . However, at longer reaction times (20–30 hours), two secondary products, 8 and 9 , were formed which resulted via subsequent dichlorocyclopropanation of 4b .