Cyclopropanes, bicyclic/spiro

Vicinally donor-acceptor-substituted olefins usually are rather unreactive species. Nevertheless cyclopropanation of 2,2-dimethyl-3(2 H)-furanone 70 could be executed with dimethyl oxosulfonium methylide as a methylene source. The bicyclic compound 71 is formed in modest yield accompanied by the spiro epoxide as a second product in almost equal amounts. Carbinols 72 derived from 71 by alkyl lithium addition can be nitrosated and photolyzed to suffer a Barton fragmentation. The resulting y-oxoaldehydes are directly cyclized to afford the 2-substituted cyclopentenones 73 in good yield 41. ... 

In Table 6, which was compiled from work on bicyclo[n.l.O]alkanes, bicyclo[1.1.0]-butanes, bicyclo[2.1.0]hexanes, bicyclo[2.2.1]heptanes , bicyclo[3.1.1]heptanes bicyclo[2.2.2]octanes ", bicyclo[3.3.0]octanes", bicyclo[4.n.0]alkanes, bicyclo[3.3.13-nonanes" spiro[4.5]alkanes" and trans-decalins the chemical shifts of several bicyclic alkanes are tabulated. The values were mainly explained by the steric effects present in the different structural environments, with the exception of fused cyclopropane rings (see below). 

A soln. of startg. (3-chloroketimine in /cr/-butanol treated with 2 eqs. KOBu-r, stirred under reflux for 12 h, after cooling the mixture diluted with pentane, and stirred for 1 h 2-methylene-3,3-dimethyl-l-phenylazetidine. Y 90%. The method is restricted to N-aryl-derivs., N-benzyl-derivs. affording cyclopropanes (Synth. Meth. 42, 952) and N-alkyl-derivs. giving p-aminoketones. F.e. inch spiro and bicyclic compds. s. P. Sulmon et al., J. Org. Chem. 53, 4462-5 (1988). 

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