Rhodium-Catalyzed Intermolecular Chelation Controlled Alkene and Alkyne Hydroacylation: Synthetic Scope of β-<i>S</i>-Substituted Aldehyde Substrates
作者:Michael C. Willis、Helen E. Randell-Sly、Robert L. Woodward、Steven J. McNally、Gordon S. Currie
DOI:10.1021/jo060582o
日期:2006.7.1
The use of β-S-substituted aldehydes in rhodium-catalyzed intermolecularhydroacylation reactions is reported. Aldehydes substituted with either sulfide or thioacetal groups undergo efficient hydroacylation with a variety of electron-poor alkenes, such as enoates, in Stetter-like processes and with both electron-poor and neutral alkynes. In general, the reactions with electron-poor alkenes demonstrate
Rhodium-Catalyzed Reductive Aldol Reactions Using Aldehydes as the Stoichiometric Reductants
作者:Michael C. Willis、Robert L. Woodward
DOI:10.1021/ja056130v
日期:2005.12.1
the addition of [Rh(dppe)]ClO4 to beta-sulfide-substituted aldehydes, can function as the stoichiometricreductants in reductive aldol processes. Unsaturated nitriles, esters, and ketones can be used as enolate equivalents, and a variety of simple alpha- and beta-substituted aldehydes can be employed. The use of a second, more electrophilic, aldehyde allows three-component reactions to be performed
Rhodium-Catalysed Intermolecular Alkyne Hydroacylation: The Enantioselective Synthesis of α- and β-Substituted Ketones by Kinetic Resolution
作者:Carlos González-Rodríguez、Scott R. Parsons、Amber L. Thompson、Michael C. Willis
DOI:10.1002/chem.201001748
日期:——
Cleared up! Intermolecularalkynehydroacylation represents a new addition to the range of transition‐metal‐catalysed hydroacylation reactions that can be performed in an enantioselective manner. By using a kineticresolution procedure, both racemic α‐ and β‐substituted aldehydes can be converted into the corresponding enantiomerically enriched substituted enone products (see scheme).
An O-substituted hydroxylamine having the following general formula:
R
1
—CHX—O—NH
2
wherein X is hydrogen or an alkyl; and R
1
is an unsubstituted or substituted phenyl, thienyl, furanyl, pyrrolyl or —CR
2
═CR
3
R
4
; wherein R
2
, R
3
and R
4
are hydrogen, halogen or alkyl. The O-substituted hydroxylamine exhibits at least one property selected from the group consisting of: essentially free of hydroxylamine; essentially free of any solvent; a water content of between about 0% to 90% by weight; and a high strength (as measured by mole of the O-substituted hydroxylamine per gram of sample) of between about 0.5 to 3.3-fold as much as a 40% O-substituted hydroxylamine salt solution, by weight. The O-substituted hydroxylamine further comprising at least one additional property selected from the group consisting of: a purity of between about 98% to 100%, based on gas chromatographic area; and a purity drop of less than about 1.2% after 78 days at 40° C. when the O-substituted hydroxylamine has a concentration of about 85% in water, based on gas chromatographic area. The O-substituted hydroxylamine is at least one isomer selected from the group consisting of cis, trans and a mixture thereof. The O-substituted hydroxylamine may also be reacidified to an O-substituted hydroxylamine salt free of hydroxylamine.