Cyclopropylcarbinyl cations complexes

Since there are three possible ways to rearrange cyclopropylcarbinyl cation (86) of the type proposed in presqualene pyrophosphate conversion, and the unwanted cyclopropylcarbinyl (86) to allyl (87) rearrangement has been found to account for 99% of total reaction flux in model studiessqualene synthetase must exert strict regiochemical control in the catalytic steps to produce the enzymatic product squalene via the kinetically and thermodynamically unfavored (ca. 0.04 % of the total non-enzymatic flux) rearrangement process (86 82). A tight enzyme-substrate complex that imposes an energy barrier... 

An ion cyclotron resonance study of ion-molecule reactions in benzene has shown that the cyclopropenyl cation arises from a a-type complex between protonated benzene and benzene. The mass spectral fragmentation of cyclopropanol monoethers has been examined and subjected to theoretical study and the fragmentation of a series of underivatized aminocyclitol-aminoglycoside antibiotics is believed to involve the ion (387). The chemical ionization mass spectrum of oct-6-en-3-one has been interpreted as involving the cyclobutyl-cyclopropylcarbinyl cation rearrangement (388)- (389). ... 

Complex mixtures were obtained and the formation of both cis and trans cyclodecenes (47 and 48) in a 3 1 ratio indicates that, contrary to the cation (vide infra, equation 71), the cyclopropylcarbinyl radical does not give a stereospecific ring expansion ... 

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