1,1′‐Linked Cyclopropane Derivatives: The Helical Conformation of Quinquecyclopropanol

Abstract

In a twist: 1,1′‐Linked oligocyclopropanols have been obtained by an iterated reaction of a cyclopropaneboronate with in situ generated lithium bromocyclopropylidenoid and subsequent oxidation. As predicted by DFT computations for sexicyclopropane (shown in blue) in the gas phase, the quinquecyclopropane unit in the 3,5‐dinitrobenzoate of quinquecyclopropanol (yellow, dinitrobenzoyl group omitted for clarity) adopts a helical conformation in the crystal.

Synthesis and properties of the ivyanes: the parent 1,1-oligocyclopropanes

“…These first X-ray crystal structures of parent ivyanes (see ESI †) confirm the B3LYP/6-31G(d) predicted (gas phase) helical conformations and are consistent with X-ray structures of substituted [3]-, [4]-and [5]ivyanes reported by de Meijere. 5 The gauche conformation between adjacent cyclopropanes means that one turn of the helix involves a five carbon chain. The composition of each crystal studied is racemic, with unit cells containing both enantiomeric structures.…”

“…Thus, in an elegant application of the Matteson homologation, de Mejiere recently reported an iterative approach that produces mixtures of alcohol-substituted 1,1-oligocyclopropanes. 5 Unfortunately, an attempt to prepare the unsubstituted systems from these substituted analogues was unsuccessful, with ring opened products being formed. 5 Very recently, we reported short preparative syntheses of the first six members of the dendralene family.…”

“…5 Unfortunately, an attempt to prepare the unsubstituted systems from these substituted analogues was unsuccessful, with ring opened products being formed. 5 Very recently, we reported short preparative syntheses of the first six members of the dendralene family. 6 Herein we report the one-step synthesis of the first six members of the unsubstituted 1,1-oligocyclopropanes from the dendralenes.…”

Selective Carbon–Carbon Bond Cleavage of Cyclopropanols

“…70 In 2007, de Meijere and co-workers prepared 1,1′oligocyclopropylcyclopropyl alcohols and studied their reactivity. 460 Treating 1,1′-oligocyclopropylcyclopropyl alcohols 1049a and 1049b with Ph 3 P•Br 2 and pyridine at low temperature affords β-bromoketones 1050a and 1050b in good yields (Scheme 228). This result was noteworthy to the authors, since the related 1-cyclopropyl-substituted cyclopropyl alcohols are converted to the corresponding cyclopropyl bromides under essentially identical conditions, and products from cascade rearrangements of the cyclopropane units were not observed.…”

“…In 2007, de Meijere and co-workers prepared 1,1′-oligocyclopropylcyclopropyl alcohols and studied their reactivity . Treating 1,1′-oligocyclopropylcyclopropyl alcohols 1049a and 1049b with Ph 3 P·Br 2 and pyridine at low temperature affords β-bromoketones 1050a and 1050b in good yields (Scheme ).…”