Convenient Access to Various 1-Cyclopropylcyclopropane Derivatives

Abstract

1-Bromo-1-cyclopropylcyclopropane (1), which is easily accessible in two steps from methyl cyclopropanecarboxylate, does not form a stable Grignard reagent upon reaction with elemental magnesium, yet it readily undergoes bromine/lithium exchange without rearrangement upon treatment with tert-butyllithium in diethyl ether/pentane at -78 degrees C, and the resulting 1-lithio-l-cyclopropylcyclopropane can be trapped with various electrophiles to give the correspondingly 1-substituted bicyclopropyl derivatives 10 in yields ranging from 38 to over 90% (13 examples). The (1-cyclopropylcyclopropyl)boronate 10m, which is also obtained from the 1-lithio derivative, has been subjected to Suzuki cross couplings with a number of aryl halides to furnish 1-aryl-1,1'-bicyclopropyl compounds 11 (4 examples, 14-50% yield), predominantly without rearrangement. Further transformations of 1-cyclopropylcyclopropanecarbaldehyde (10e) have provided 2-(1-cyclopropylcyclopropyl)glycine (16), ethyl 3(1-cyclopropylcyclopropyl)acrylate (17), and its cycloadducts with the nitrone 18 and cyclopentadiene 19, albeit the latter only in poor yield.