Tandem radical reactions of N,N-diphenylhydrazones. Studies with chiral hydrazones.

Abstract

Alkyl radicals, generated with tributyltin hydride from their haloprecursors, are trapped efficiently by carbon monoxide under pressure, and the resulting acyl radicals undergo rapid cyclization onto N,N-diphenylhydrazones to yield alpha-hydrazinocyclopentanones. Selective reduction of the resulting ketones provided the corresponding cis- or trans-beta-hydrazinoalcohols, such as 282a--283b. A novel rearrangement was uncovered when the corresponding alpha-carbonyl hydrazine was treated with Lewis acids to afford product 292. Attempted carbonylation of aminyl radicals failed to provide the expected products. Tandem radical reactions were employed for the synthesis of the bicyclic ring system 359. The monocyclized products 362 and 363 were also formed. Attempted synthesis of tropane analogs via tandem radical reactions resulted only in the formation of the 7-membered ring products, such as 406. The level of asymmetric induction in radical carbocyclizations mediated by the presence of hydrazone chiral auxiliaries, such as 417 and 418 was examined.* *Please refer to dissertation for diagrams.