Reaction of certain geometrically defined 1,1-dioxy-4-alkyl- and -4,4-dialkyl-substituted buta-1,3-dienes with halogenated quinones does not involve Diels-Alder or Michael addition chemistry. Instead, rapid competitive oxidation of the dienes to give 2,4-dienoate esters was observed. This new reaction involves strong spatial association between diene and quinone, hydrogen being transferred specifically from the (4E)-alkyl group. Its scope is compared with addition of the same terminally substituted dienes towards the reactive non-quinonoid dienophile tetracyanoethylene.
Reaction of certain geometrically defined 1,1-dioxy-4-alkyl- and -4,4-dialkyl-substituted buta-1,3-dienes with halogenated quinones does not involve Diels-Alder or Michael addition chemistry. Instead, rapid competitive oxidation of the dienes to give 2,4-dienoate esters was observed. This new reaction involves strong spatial association between diene and quinone, hydrogen being transferred specifically from the (4E)-alkyl group. Its scope is compared with addition of the same terminally substituted dienes towards the reactive non-quinonoid dienophile tetracyanoethylene.
Highly Diastereoselective Three-Component Vinylogous Mannich Reaction between Isoquinolines, Acyl/Sulfonyl Chlorides, and Silyloxyfurans
作者:Philippe Hermange、Marie Elise Tran Huu Dau、Pascal Retailleau、Robert H. Dodd
DOI:10.1021/ol901452d
日期:2009.9.17
Reaction of an isoquinoline, a silyloxyfuran, and an acyl or sulfonylchloride provides easy access to a wide variety of isoquinolinobutyrolactones with excellent yields and diastereoselectivites (R*,R* isomer), even in the case of formation of quaternary centers (i.e., R3 or R4 = Me). Moreover, the use of a chiral auxiliary allowed formation of a single stereoisomer in 96% yield. This represents the
Enolisation of αβ-unsaturated esters : regio- and geometrical control
作者:Donald W. Cameron、Mark G. Looney、Judy A. Pattermann
DOI:10.1016/0040-4039(95)01531-0
日期:1995.10
LDA-Mediated γ-deprotonation of simple αβ-unsaturatedesters occurs (Z)- to the ester group; silylation then leads to oxy butadienes with strong regio- and geometrical selectivity.
[reaction: see text]. The use of the Z-configured vinylogous silyl ketene acetals in Mukaiyamaaldolreactions is described. Isopropyl alcohol as scavanger and the use of tris(pentafluorophenyl)borane as the Lewisacid are required for obtaining the gamma-alkylated syn-product selectively. In cases of alpha-chiral aldehydes, Felkin-Anh selectivity was observed.
A One-Pot Non-Aldol-Aldol Vinylogous Mukaiyama Aldol Tandem Sequence for the Rapid Construction of Polyketide Frameworks
作者:Markus Kalesse、Nicola Rahn
DOI:10.1055/s-2005-863743
日期:——
The rapid assembly of polyketide segments remains one central task in the field of natural product synthesis. Besides the stereoselective assembly of carbon frameworks functional group transformations and protecting group manipulations have to be optimized in order to streamline organic synthesis. The activated aldehyde derived from Jung’s non aldol-aldol method serves as an intermediate for the subsequent vinylogous Mukaiyama aldol reaction.
Reaction of certain geometrically defined 1,1-dioxy-4-alkyl- and -4,4-dialkyl-substituted buta-1,3-dienes with halogenated quinones does not involve Diels-Alder or Michael addition chemistry. Instead, rapid competitive oxidation of the dienes to give 2,4-dienoate esters was observed. This new reaction involves strong spatial association between diene and quinone, hydrogen being transferred specifically from the (4E)-alkyl group. Its scope is compared with addition of the same terminally substituted dienes towards the reactive non-quinonoid dienophile tetracyanoethylene.