Regioselective Functionalization. 7.1 Unexpected Preferences for Bridgehead Migration in Schmidt Rearrangement Syntheses of Novel 2,6-Diazabicyclo[3.2.x]alkan-3-ones (x = 1−3)

Autor:	Steven W. Szczepanski, Yushi Xiao, Jing Yuan, Nian Liu, Askia Sheikh, Jee Y. Kim, Grant R. Krow
Rok vydání:	1999
Předmět:	chemistry.chemical_classification chemistry.chemical_compound Ketone chemistry Bicyclic molecule Stereochemistry Organic Chemistry Regioselectivity Surface modification Schmidt reaction Methylene
Zdroj:	The Journal of Organic Chemistry. 64:1254-1258
ISSN:	1520-6904 0022-3263
Popis:	Regioselective syntheses of 2,6-diazabicyclo[3.2.x]alkan-3-ones (x = 1−3) 34 by insertion of nitrogen next to the bridgehead (BH) of 2-azabicyclo[2.2.x]alkanones 32 with hydroxylamine-O-sulfonic acid are described. The ketones 32 under Schmidt reaction conditions (HN3/H2SO4) afford major amounts of BH migrated lactams 34 but also, when x = 2 or 3, the methylene (M) migrated lactams, 3,6-diazabicycl[3.2.x]alkan-2-ones 37. The present N-insertion reactions favoring BH migration with azabicyclic ketones contrast markedly with reactions of the related carbocycles 1a,b, which give only methylene migrated lactams 2a,b with HN3/H2SO4. Schmidt reactions of 3-anti/syn-methyl- and 3-anti-phenyl-2-azabicyclo[2.2.2]octan-5-ones 17, 20, and 23 (64:36 ± 9, BH:M) follow the reaction pattern of the parent ketone 14, but the 3-syn-phenyl ketone 26 gives major (65%) methylene migration. The results offer insights into the BH vs M migration dichotomy for the Beckmann and Schmidt reactions of bridged bicyclic ketones.
Databáze:	OpenAIRE
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