Reaction behavior of cyclopropylmethyl cations derived 1-phenylselenocyclopropylmethanols with acids

Reactivity and mechanism in the ring-opening of cyclopropylmethylplatinum(IV) complexes

“…Transition metal complexes containing cyclopropylmethyl or cyclobutylmethyl ligands are often invoked as reaction intermediates in these reactions, and the products may contain either the intact cycloalkyl ring or a ringopened form [1,2]. The transition metal may play a direct role in the ring-opening step, but it is also well known that cyclopropylmethyl to butenyl isomerisation may occur within the organic free radicals, cations or anions [3][4][5][6]. Some insights into the mechanisms have been gained by study of stoichiometric reactions, but there are still surprisingly few known examples of thermally stable transition metal complexes with cyclopropylmethyl or cyclobutylmethyl ligands to act as model compounds [7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…Thus, the reaction of [PtMe 2 (bipy)], 1, with a 20-fold excess of a 1:1 mixture of cyclopropylmethyl and cyclobutylmethyl bromides gave complex 2, with none of complex 3 detectable by 1 H NMR. The large neighboring group effect of the cyclopropyl substituent [25][26][27] and the absence of ring opening during the oxidative addition [3][4][5][6] both support an S N 2 mechanism of oxidative addition [28,29]. The 2-butenyl bromide was an 85:15 mixture of E and Z isomers and the ratio of products 5:6 was 80:20, indicating that the alkene stereochemistry is retained during the oxidative addition and that the Z-2-butenyl bromide reacts slightly faster.…”

Synthesis of Allenes by 1,2-Elimination

“…Honda et al reported that vinyl selenides 20 can be oxidized with m-CPBA and then undergo enantiospecific syn-selenoxide elimination to form diastereoisomerically pure allenes 22 (Scheme 5c). [13] Scheme 5. Asymmetric synthesis of allenes by selenoxide elimination Frantz and co-workers have reported a new method for the enantioselective synthesis of disubstituted allenes by palladium catalyzed β-hydride elimination (Scheme 6).…”

Stereocontrolled Synthesis and Functionalization of Cyclobutanes and Cyclobutanones

“…Moreover carbocyclic ring opening is possible and it represents an advantageous synthetic route to acyclic compounds [6]. Cyclobutane and cyclobutanone derivatives can be easily prepared by reliable synthetic methods [7] such as [2+2] cycloadditions, [8,9] cyclopropanol- [10,11], cyclopropylphenylthio- [12,13,14,15] and selenium-carbinols ring expansions [16,17,18] or ring enlargement of oxaspiropentanes [19,20,21]. A large number of papers and patents have been published in this area.…”