No abstract

Methyl -and phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6 have been prepared by photoirradiation of appropriately substituted 1,2-dihydropyridines. Torquoselectivity is observed in the synthesis of the 3-endo-methyl-and 3-endo-phenyl-2-azabicyclo[2.2.0]hexenes 6c-e from 2-methyl-and 2-phenyl-1,2-dihydropyridines 5c-e. Products formed upon addition of bromine to 3-endo-, 4-, and 5-methyl-and 3-endo-phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 6a-f were substituent dependent. For 6a,b, which lack substituents at C 3 or C 5 , mixtures of unrearranged dibromides 8a,b and rearranged dibromides 9a,b were obtained. With the 3-endo-substituents in 6c-e, only rearranged dibromides 9c-e were formed; 5-methyl substitution afforded mainly unrearranged dibromide 8f and some allylic bromide 10. Both unrearranged 5-endo,6-exo-dibromo-2-azabicyclo[2.2.0]hexanes 8 and rearranged 5-anti-6-anti-dibromo-2-azabicyclo[2.

Hydroxylamine-O-sulfonic acid reacted with syn-7-X- and anti-7-Y-substituted norcamphor derivatives [X = H, OMe, Cl, Br, OTos; Y = H, COOMe, Cl, Br, Tos, COOMe(5-exo-Br)], to give solely bridgehead migrated 2-azalactams, except for minor amounts of methylene migrated 3-azalactams from norcamphor (1) and the syn-7-Br ketone 19. Schmidt reactions of the same ketones provided varying mixtures of methylene and bridgehead migrated lactams, except for norcamphor (1) and anti-7-Br ketone 31, which provided solely 3-azalactams. Significant ratios (>0.4) of bridgehead migration to cleavage products were observed in the Schmidt reactions only with 7-OTos ketones 22 and 24 with exo-5-bromo-anti-7-methoxycarbonyl ketone 37. The Schmidt rearrangements most likely involve iminodiazonium ion intermediates in light of the large amounts of cleavage observed relative to lactam formation and the insensitivity of methylene migration to the substituent size in the reactions of syn-7-substituted norcamphors.