Cracked under strain: Strained allylic cyclobutanols and cyclopropanols readily undergo a ring expansion described by the title rearrangement. This reaction is promoted by catalytic amounts of 1 and displays high tolerance with respect to the substrate scope. The corresponding β‐fluoro spiroketone products are isolated in high yields and with excellent stereoselectivities. EDG=electron‐donating group
The present manuscript describes a high-yielding enantioselective semipinacol transposition, initiated by an electrophilic iodination event. The title transformation makes use of the anionic phase-transfer catalysis (PTC) paradigm for chirality induction. Thus, when combined appropriately, the insoluble cationic iodinating reagent S9 and the lipophilic phosphoric acid L9 act as an efficient source
Visible‐Light Photoredox‐Catalyzed Semipinacol‐Type Rearrangement: Trifluoromethylation/Ring Expansion by a Radical–Polar Mechanism
作者:Basudev Sahoo、Jun‐Long Li、Frank Glorius
DOI:10.1002/anie.201503210
日期:2015.9.21
semipinacol‐type rearrangement proceeding via 1,2 alkyl migration was developed. In this transformation, trifluoromethylation of the CC bond of α‐(1‐hydroxycycloalkyl)‐substituted styrene derivatives is followed by ringexpansion of the 1‐hydroxycycloalkyl group to deliver novel cycloalkanones with all‐carbon quaternary centers. The reaction proceeds via a radical–polar mechanism, with trifluoromethylation
accomplished with a chiral Lewis base and a chiral Brønsted acid as cocatalysts, generating various β-arylthio ketones bearing an all-carbon quaternary center in moderate to excellent yields and excellent enantioselectivities. These chiral arylthio ketone products are common intermediates with many applications, for example, in the design of new chiral catalysts/ligands and the totalsynthesis of natural products
electrophilic thiocyano semipinacolrearrangement of allylic alcohols has been achieved for the first time by using N-thiocyano-dibenzenesulfonimide (NTSI). This approach provides a direct, simple, and efficient strategy for the formation of thiocyano carbonyl compounds with moderate to excellent yields. Meanwhile, an all-carbon quaternary center was rapidly constructed. In addition, an asymmetric version of this