Experimental antiulcer drugs. 3. Some unusual transformations of the cyclopenta[ c ] pyrroles

The cyclopenta[ c ]pyrrole‐4‐carbonitrile ( 3 ) is transformed by hyrlroxylamine in hot alcohol to 4,5,6,6a‐tetrahydro‐l‐imino‐3,5,5,6a‐tetramethyl‐4‐cyclopenta[ c ]pyrrole methyl ketone oxime ( 5 ) in contrast to the cyclopentapyrrole 10 which afforded 1,2‐diacetyl‐3,3,5,5‐tetramethyl‐cyclopentene dioxime ( 11 ). The cyclopenta[ c ]pyrrole‐4‐carboxamide 1 ( R = C 6 H 5 ) yielded the isomeric 2a,3,4,4a,5,6,6a,6b‐octahydro‐2a,4,4,6a‐tetramethyl‐5‐(phenylimino)pentaleno[1,6‐ bc ]‐pyrrol‐2‐(1 H )one ( 12 ) in hot dilute hydrochloric acid or hot 99% phosphoric acid. The amide 1 (R = C 6 H 5 ) was transformed in the solid state by oxygen over a period of several months to a mixture of the isomeric anils, 13 and 14 of 1,7‐diacetyl‐7‐hydroxy‐4,6,6‐trimethyl‐2‐azabicyclo‐[2.2.l.]heptan‐3‐one( 16 ).