Carboxylate-directed C–H allylation with allyl alcohols or ethers
作者:Xiao-Qiang Hu、Zhiyong Hu、A. Stefania Trita、Guodong Zhang、Lukas J. Gooßen
DOI:10.1039/c8sc01741g
日期:——
A [Ru(p-cymene)Cl2]2 catalyst activates allylalcohols and ethers for the regioselective ortho-C–H allylation of aromatic and heteroaromatic carboxylates. The reaction is orthogonal to most C–H functionalisations with allylalcohols in that allyl arenes rather than carbonyl compounds are obtained. A wide range of substrates are thus smoothly transformed to allylarenes at 50 °C in phosphate-buffered
A photo-semipinacol rearrangement of unactivated allylic alcohols is reported. Aliphatic as well as aromatic groups participate as migrating groups, yielding a variety of α,α-disubstituted ketones. The operationally simple conditions prescribe 1 mol % benzothiazinoquinoxaline as organophotocatalyst, 0.5 mol % Co-salen, and 10 mol % lutidinium triflate and, importantly, display reactivity complementary
Various 1-phenylbut-3-enylidenes, (Ph)CCR2CH=CHR', were generated thermally and photolytically from tosylhydrazone (diazo) precursors. 1,2-Vinyl shifts, leading to 1,3-dienes, R'CH=CHC(Ph)=CR2, were found to predominate over gamma-C-H insertion (R = Me) and to compete with 1,2-H shifts (R = H). Intramolecular addition to the double bond was detected in the case of R = R' = Me. The resulting bicyclobutane is thermally stable and does not mediate the vinyl shift. Stereospecific migration of 1-propenyl groups (R' = Me), with retention of configuration, was observed on thermolysis and direct photolysis of appropriate substrates. These data exclude the intervention of a triplet diradical and point, to vinyl migration in the singlet manifold. Benzophenone-sensitized generation of the carbenes led to partial stereomutation but did not provide conclusive evidence for a triplet rearrangement (isomerization of the diene products could not be avoided under these conditions).
Hayashi, Sayuri; Yorimitsu, Hideki; Oshima, Koichiro, Journal of the American Chemical Society, 2009, vol. 131, p. 2052 - 2053
Use of cis-dichloro[(S)-α-methylbenzylamine](ethylene)Pt(II) as a chiral derivatizing agent for the determination by 195Pt-NMR of the enantiomeric composition of unsaturated ethers or alcohols having a quaternary chiral carbon atom
cis-Dichloro[(S)-α-methylbenzylamine](ethylene)platinum(II) is an efficient chiralderivatizing agent for the determination, by 195Pt-NMR spectroscopy, of the enantiomericcomposition of unsaturated ethers and alcohols having a quaternary chiral carbon atom.