Synthesis of novel 2-azabicyclo[2.2.0]- and [2.1.1]hexanols

Methyl- and phenyl-substituted N-(ethoxycarbonyl)-2-azabicyclo [2.2.0]hex-5 -enes 6 were reacted with NBS in wet DMSO to afford bromohydrins. Mixtures of unrearranged 6-exo-bromo-5-endohydroxy-2-azabicyclo [2.2.0] hexanes 7a,b and rearranged 5-anti-bromo-6-anti-hydroxy-2-azabicyclo [2.1.1]hexanes 8a, b were formed stereoselectively from the parent alkene 6a and 4-methyl alke ne 6b. The 5-methyl alkene 6c affords only unrearranged bromohydrin 7c and dibromohydrin 9. By contrast, solely rearranged 3-endo-substituted-2-azabic yclo[2.1.1]hexane bromohydrins 8d-f result from additions to S-endo-methyl alkene ed, 3-endo-4-dimethyl alkene 6e, and 3-endo-phenyl alkene 6f. As an alternative route to bromohydrins, the parent 5,6-exo-epoxide 10a and 5-end wo-methyl-5,6-exo-epoxide 10b were ring opened with bromine/triphenylphosph ine to afford unrearranged 5-endo-bromo-6-exo-hydroxy-2-azabicyclo [2.2.0]h exanes 11a,b, while the S-endo-methyl epoxide 10c afforded solely the rearr anged 5-anti-bromo-6-anti-hydroxy-3-exo-methyl-2-azabicyclo [2.1.1]hexane i somer 8g. Tributyltin hydride reduction of bromohydrins 7a,b and 11a afford ed novel 2-azabicyclo[2.2.0]hexan-5-ols 13a,b and -6-ol 14, and bromohydrin s 8a,b, 8d-g afforded new 2-azabicyclo[2.1.1]-hexan-5-ols 15a,b and 15d-g.