A. P. Marchand, K. Ramanaiah, S. Bott
Nov 4, 1996
Citations
0
Influential Citations
5
Citations
Journal
Tetrahedron Letters
Abstract
Abstract The reactive intermediates produced via base-promoted reactions of N -tosyl- and N -benzhydrylazetidin-3-one ( 8a and 8b , respectively) with diethyl diazomethylphosphonate (DAMP) have been shown to be vinylidenecarbenes rather than the corresponding cycloalkynes. Thus, N -tosylazetidin-3-ylidenecarbene ( 9a ) was trapped in situ by cyclohexene to afford a cycloadduct, N-p- toluenesulfonyl-2-(7′-bicyclo[ 4 .1.0]heptanylidene)azetidine ( 10 ), whose structure subsequently was established unequivocally via single crystal X-ray structural analysis. These results contrast with that reported previously for the corresponding carbocyclic system (i. e., cyclobutanylidenecarbene-cyclopentyne); in the carbocyclic system, the cycloalkyne (rather than the vinylidenecarbene) is trapped in situ . The results of semi-empirical MO calculations (AM1 Hamiltonian) for ring expansion of azetidinylidenecarbenes to azacyclopentynes offer clues to the observed difference between the behavior of the heterocyclic and carbocyclic systems.