Azabicyclic Alkenes

Bn = benzyl, Boc = ferf-butyloxycarbonyl, Ts = 4-toluenesulfonyl, Ns= ferf-nitrobenzenesulfonyl 

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The anti -stereocontrolled alkylative ring-opening reaction of azabicyclic alkenes has been reported.100 iV-(2-Pyridyl)sulfonylazabenzonorbornadiene (36) has reacted with Grignard reagents in the presence of catalytic amounts of CuCN to afford, in good yields and excellent anti selectivity, the corresponding dihydronaphthalene-1-amines (37) (Scheme 20). 

Progress in transition metal-catalyzed asymmetric ring-opening reactions of azabicyclic alkenes 12CJ0433. 

Ring-Opening meso-Azabicyclic Alkenes with Nitrogen-Based Nucleophiles 419... 

Carbozincation of oxabicyclic and azabicyclic alkenes can be controlled to proceed without p-heteroatom elimination using a derivative of dppbz as ligand (Scheme 4-273). The intermediate zinc organyl can be quenched with acid or treated with an electrophile. The latter gives the corresponding cis-disubstituted heterobicycloalkane. ... 

Reactions of this type are mostly performed with internal nucleophiles attached to the carbon atom adjacent to the iminium nitrogen, thus leading to tropane-like azabicyclic systems. Both allyl- and propargylsilanes, activated and unactivated alkenes, and ketones have been successfully used as nucleophiles. The products 1 and 2 are also obtained via two consecutive C —C bond-forming reactions in a single operation. 

Steve Martin of UT Austin has reported (J. Org. Chem. 68 8867,2003) a detailed study of the synthesis of bridged azabicyclic structures via ring-closing alkene metathesis. Some examples of his work include the conversion of 12 to 13, efficiently forming six, seven and eight membered rings. He also demonstrated five-membered ring formation with the conversion of 14 to IS, which has the cocaine skeleton. 

The enantioselective synthesis of azabicyclic y-lactams starting from 2-azanorbornenones after treatment of a catalytic amount of RuCl2(PCy3)2 (= CHPh) in the presence of ethylene or allyl acetate proceeds also via ring rearrangement—alkene metathesis (ROM-CM-RCM) [41] (Scheme 19). If n = 0 or 3, no RCM occurs and a cyclic dialkenyl compound is formed by cascade ROM-CM reactions. 

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