to excellent yields with high levels of stereoselectivity. Useful C3-unit elongation, which makes the best use of an allylether as a protecting group and a nucleophilic allylation agent, is demonstrated. Mechanisms for the umpolung reaction (of an allylether into an allylic anion) and stereoselectivity associated with allylation of aldehydes are discussed.
An efficient and extremely mild method for protecting alcohols as 2-tetrahydrofuranyl ethers
作者:Jenny M Barks、Bruce C Gilbert、Andrew F Parsons、Bala Upeandran
DOI:10.1016/s0040-4039(00)01045-5
日期:2000.8
Reaction of primary or secondary alcohols with BrCCl3 and tetrahydrofuran, usually in the presence of 2,4,6-collidine, leads to the formation of 2-tetrahydrofuranyl ethers in good to excellent yield (56-92%). The reaction mechanism is believed to involve a free-radical chain reaction. (C) 2000 Elsevier Science Ltd. All rights reserved.
TSUTSUI, HIRONORI;MUTO, MASAKAZU;MOTOYOSHI, KATSUYUKI;MITSUNOBU, OYO, CHEM. LETT.,(1987) N 8, 1595-1598
Treatment of different types of alcohols with tetrahydrofuran (THF) in the presence of VCl3 and CCl4 smoothly afforded the corresponding THF-based acetals in excellent yields. The reaction is fast at room temperature, and several functional groups are tolerated, with no racemization being observed. A radical mechanism, based on Cl3C. as the active species, is proposed for this novel kind of transformation
Pd-Catalyzed Nucleophilic Alkylation of Aliphatic Aldehydes with Allyl Alcohols: Allyl, 2-Tetrahydrofuryl, and 2-Tetrahydropyranyl Ethers as Useful C3, C4, and C5 Sources