Syntheses of N-substituted 3,3,4-triphenyl-4-benzoylazetidin-2-ones and 3′,3′-diphenyl spiro(acenaphthen-1-one-2,4′-azetidin-2′-ones); novel examples exhibiting a high reactivity of imino group in ketoimines

The reaction of 2-diazo-1,2-diphenylethanone (1) with 2-imino-1,2-diphenylethanones 2a–e gave new N-substituted 3,3,4-triphenyl-4-benzoylazetidin-2-ones 3a–e, together with 1,1′,2,2′-tetraphenyl-2,2′-azinodiethanone (4). Similar reaction of 1 with 2-iminoacenaphthenones 6a, b yielded N-substituted 3′,3′-diphenyl spiro(acenaphthen-1-one-2,4′-azetidin-2′-ones) 7a, b and ketazine 4. Lithium aluminium hydride reduction of azetidinones 3a, b gave 4-α-hydroxybenzylazetidin-2-ones 5a, b. The spiro azetidinones 7a, b on reduction with sodium borohydride yielded spiro(1-hydroxyacenaphthene-2,4′-azetidin-2-ones) 8a, b. The azetidinones 3a–e and 7a, b were found to be unaffected by either acid or base hydrolysis. The marked selective reactivity of the imino group as compared to the carbonyl group towards diphenylketene has been observed in the present studies. The comparative reactivity of carbonyl groups present in azetidinones 3a, b and 7a, b has been presented.