Gold(I)-Catalyzed Formation of Bicyclo[4.2.0]oct-1-enes
摘要:
Gold(I) catalysts effectively promote the Cope rearrangement of acyclic 1,S-dienes bearing a terminal cyclopropylidene. When this methodology is applied to cyclic substrates an unexpected transformation occurs, resulting in the formation of a tricyclic compound incorporating a bicyclo[4.2.0]oct-1-ene core, a portion of which is found in a number of natural products. Density functional theory calculations (M06 and M06-2X) reveal insight into the mechanism and thermodynamics of this unique transformation.
Formation of Quaternary Stereogenic Centers by Copper-Catalyzed Asymmetric Conjugate Addition Reactions of Alkenylaluminums to Trisubstituted Enones
作者:Daniel Müller、Alexandre Alexakis
DOI:10.1002/chem.201302856
日期:2013.11.4
undergo asymmetric copper‐catalyzedconjugateaddition (ACA) to β‐substituted enones allowing the formation of stereogenic all‐carbon quaternary centers. Phosphinamine–copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β‐substituted
Chemistry of substituted (2-butene-1,4-diyl)magnesium: a facile approach to complex carbocycles, functionalized ketones and alcohols, and silicon-containing heterocycles
作者:Reuben D. Rieke、Heping Xiong
DOI:10.1021/jo00009a034
日期:1991.4
Highly reactive magnesium reacts with a wide variety of substituted 1,3-dienes to give the corresponding substituted (2-butene-1,4-diyl)magnesium complexes. Reactions of symmetrical (2-butene-1,4-diyl)magnesium with alpha,omega-alkylene dihalides form three-, four-, five-, and six-membered carbocycles. Significantly, the cyclizations are always stereospecific and completely regioselective. Depending on the initial 1,3-diene and specific electrophiles, uncyclized products can be obtained. Stepwise reactions of (2,3-dimethyl-2-butene-1,4-diyl)magnesium with two different electrophiles afford polyfunctionalized ketones with the generation of a quaternary center. Formal 1,2-additions can be effected in this manner. Substituted five- and six-membered cyclic ketones can also be synthesized in one step by this approach. Treatment of unsymmetrical (2-butene-1,4-diyl)magnesium complexes with triorganosilyl chlorides followed by cyclohexanone results in additions across a terminal double bond with high regioselectivity. Silicon-containing heterocycles or spiro compounds can be readily synthesized by using the bis-Grignard reagents.