2-CHLORO-2-CYCLOPROPYLIDENACETATE IN SYNTHESIS ll: FACILE CONSTRUCTION OF VARIOUS SPIROCYCLOPROPANE ANELLATED HETEROCYCLES

Article abstract of DOI:10.1016/S0040-4020(01)80123-X

Methyl 2-chloro-2-cyclopropylidenacetate (1a) reacts with 1,2- and 1,3-bidentate nucleophiles in a heterogeneous system of solid base and dichloromethane under phase transfer catalysis.Spirocyclopropane anellated heterocyclic carboxylates 7, 9, 14, 10, 11 were obtained with KOH from 2-aminothiophenol, 1,2-dihydroxybenzene, 1,3-propanedithiol and with K2CO3 from 2-aminophenol and 2-aminoethanethiol respectively.With KOH the latter gave the seven-membered lactam 13, and 2-aminophenol led to methyl 4-benzoxazolylbutyrate 12.The adduct of benzylamine to the t-butyl ester 1b in a three-step sequence yielded the β-lactame 24 and an isomericcompound , probably the imido-β-lactone E/Z-25.Following a similar strategy, i.e. a sequence of Mukaiyama type alkylation, substitution, functional group interconversion and cyclization, 1a was converted to the cyclic imine 29a which served as a precursor to the carbapenam derivative 31.Finally, a few examples of 1,3-dipolar cycloaddition onto 1a are reported.Diazomethane added regioselectively in the "normal", diphenyl-diazomethane in the opposite mode to yield pyrazolines 33a and 34a respectively; 2-diazopropane gave both regioisomeric pyrazolines.The primary cycloadduct of nitrilylid 35 and 1a could not be isolated but rather the pyrrole derivative 38 derived by ring-opening rearrangement.