yields (up to 99 %) and excellent diastereo- (up to >99:1 dr) and enantioselectivities (up to 95 % ee) using a low catalyst loading. Most importantly, these results show that the concept of DNA-basedasymmetriccatalysis can be expanded to new synthetic transformations offering an efficient, sustainable, and highly selective tool for the construction of chiral building blocks.
Asymmetric Ni-Catalyzed Conjugate Allylation of Activated Enones
作者:Joshua D. Sieber、James P. Morken
DOI:10.1021/ja710922h
日期:2008.4.1
The nickel-catalyzedenantioselective addition of allylboronic acid pinacol ester, allylB(pin), is described. This reaction is highly effective with dialkylidene ketones and favors the allylation of the benzylidene site in nonsymmetric substrates. The reaction appears to proceed by conversion of the dialkylidene ketone substrate to an unsaturated pi-allyl complex (I), followed by reductive elimination
3,5-Bis(trifluoromethyl)phenyl Sulfones for the Highly Stereoselective Julia–Kocienski Synthesis of α,β-Unsaturated Esters and Weinreb Amides
作者:Diego A. Alonso、Mónica Fuensanta、Enrique Gómez-Bengoa、Carmen Nájera
DOI:10.1002/ejoc.200800041
日期:2008.6
l)phenyl (BTFP) sulfones tert-butyl α-(BTFPsulfonyl)acetate (4) and Weinreb α-(BTFPsulfonyl)acetamide (5) have successfully been employed in the Julia–Kocienski olefination of aldehydes with K2CO3 as the base at 120 °C in DMF under solid/liquid phase-transfer catalysis conditions to afford α,β-unsaturated esters and Weinrebamides, respectively. The corresponding products were obtained in good yields
New Reagent for Convenient Access to the α,β-UnsaturatedN-Methoxy-N-methyl-amide Functionality by a Synthesis Based on the Julia Olefination Protocol
作者:Beedimane Narayana Manjunath、Neeraj P. Sane、Indrapal Singh Aidhen
DOI:10.1002/ejoc.200600126
日期:2006.6
A newreagent for the synthesis of the α,β-unsaturated N-methoxy-N-methyl-amide structural unit has been developed. 2-(Benzo[d]thiazol-2-ylsulfonyl)-N-methoxy-N-methylacetamide, a crystalline solid with an indefinite shelf life that can be easily prepared in two convenient steps from 2-chloro-N-methoxy-N-methylacetamide, reacted with a variety of aldehydes under Julia conditions to furnish the α,β-unsaturated
Synthesis of α,β-Unsaturated α′-Haloketones through the Chemoselective Addition of Halomethyllithiums to Weinreb Amides
作者:Vittorio Pace、Laura Castoldi、Wolfgang Holzer
DOI:10.1021/jo401236t
日期:2013.8.2
A straightforward synthesis of variously functionalized α,β-unsaturated α′-haloketones has been achieved through the chemoselective addition of halomethyllithium carbenoids to Weinrebamides at −78 °C. A comparative study employing the corresponding esters under the same reaction conditions pointed out that the instability of the tetrahedral intermediate formed from the latter is responsible for the