Catalytic Asymmetric Reactions for Organic Synthesis: The Combined C−H Activation/Siloxy-Cope Rearrangement
摘要:
Tetrakis(N-[4-dodecylbenzenesulfonyl]-(L)-prolinate) dirhodium [Rh-2(S-DOSP)(4)]-catalyzed decomposition of vinyldiazoacetates in the presence of allyl silyl ethers results in the formation of the direct C-H insertion product and the product derived from a combined C-H activation/siloxy-Cope rearrangement. Both products are formed with very high diastereoselectivity (>94% de) and high enantioselectvity (78-93% ee). Under thermal or microwave conditions, the direct C-H insertion product undergoes a siloxy-Cope rearrangement in a stereoselective manner.
The Stereochemical Course of Intramolecular Michael Reactions
作者:Eugene E. Kwan、Jonathan R. Scheerer、David A. Evans
DOI:10.1021/jo302138z
日期:2013.1.4
We present a general model for understanding the stereochemicalcourse of intramolecular Michael reactions. We show that the addition of β-ketoester enolates to α,β-unsaturated esters and imides bearing adjacent stereocenters (X, Y = H, Me, OR) leads to high levels of asymmetric induction. Reinforcing and nonreinforcing stereochemical relationships are evaluated from the syn and anti reactant diastereomers
Enantiopure piperidines 4 may be accessed in very good overall yields and high stereoselectivity from the bifunctional products 2 of the silyloxyCoperearrangement of chiralaldolproducts 1 by sequential nucleophilic addition of primary amines and subsequent hydrogenation. The reaction is proposed to proceed by initial imine formation followed by an intramolecular aza-conjugate addition to the α