Mild and Stereoconvergent Palladium-Catalyzed Carbonyl Alkenation Reaction of α,β-Unsaturated Aldehydes

Abstract

The addition of preformed ketone and ester enolates to a,bunsaturated aldehydes 1 followed by in situ protection leads to the carbonates 3, 7, 8, 11, and 13. They are converted into sensitive functionalized dienes 4, 9, 12, and 14 by a smooth palladiumcatalyzed elimination. Both syn-and anti-carbonates 7 and 8 lead to E-dienes 9 in a stereoconvergent manner.

Synthesis and Characterization of Cyanobutadiene Isomers—Molecules of Astrochemical Significance

“…Rather, the sensitivity of 1 to undergo reaction (dimerization, polymerization) or degradation (heat, light, strong bases, and silica/alumina gels) greatly complicates the task of purifying and characterizing 1. Our attempts to replicate the procedure reported by Braun et al 55 (Scheme 1e) failed to produce an isolable amount of the expected mixture of diastereomers. In our hands, the procedure described by Clary and Back 56 (Scheme 1f) afforded E-1 and Z-1 as components in a rather complex mixture of products.…”

“…Previous Syntheses of 1-Cyano-1,3-butadiene (1) a a (a) Carothers and Berchet; 38 Coffman. 39 (b) Snyder et al 41 (c) Daessle et al 48 (d) Katagiri et al 53 (e) Braun et al 55 (f) Clary and Back. 56 (g) Banert.…”

Synthesis and Characterization of Cyanobutadiene Isomers—Molecules of Astrochemical Significance

“…Rather, the sensitivity of 1 to undergo reaction (dimerization, polymerization) or degradation (heat, light, strong bases, and silica/alumina gels) greatly complicates the task of purifying and characterizing 1. Our attempts to replicate the procedure reported by Braun et al 55 (Scheme 1e) failed to produce an isolable amount of the expected mixture of diastereomers. In our hands, the procedure described by Clary and Back 56 (Scheme 1f) afforded E-1 and Z-1 as components in a rather complex mixture of products.…”

“…Previous Syntheses of 1-Cyano-1,3-butadiene (1) a a (a) Carothers and Berchet; 38 Coffman. 39 (b) Snyder et al 41 (c) Daessle et al 48 (d) Katagiri et al 53 (e) Braun et al 55 (f) Clary and Back. 56 (g) Banert.…”

Evidence for Competing syn and anti Pathways in Palladium-Catalyzed Eliminations of Acyclic Allylic Carbonates

“…[15] In this context, the idea came up to use carbonates derived from diastereomeric aldols as a suitable probe for the elucidation of the stereochemical outcome in palladium-catalyzed eliminations. For this purpose, lithium enolates derived from 2',4',6'-trimethylpropiophenone 5 were added to (E)-crotonaldehyde, and the lithium alkoxide formed thereby was converted in situ into the diastereomeric carbonates 6 a and 6 b upon treatment with methyl chloroformate (Scheme 2).…”

Atropisomeric benzamides and naphthamides as chiral auxiliaries †

“…The anti-selective aldol reactions of hindered aryl esters appear as key steps in synthetic routes to davanone, 23 lankanolide, 24 the pamamycins, 25 erythronolides A 26 and B 27 and the vitamin E side chain, 28 among others. 29,30 Scheme 1 anti-Aldol reactions with hindered phenyl esters.…”

Synthesis and Characterization of Cyanobutadiene Isomers—Molecules of Astrochemical Significance

“…Rather, the sensitivity of 1 to undergo reaction (dimerization, polymerization) or degradation (heat, light, strong bases, and silica/alumina gels) greatly complicates the task of purifying and characterizing 1. Our attempts to replicate the procedure reported by Braun et al 55 (Scheme 1e) failed to produce an isolable amount of the expected mixture of diastereomers. In our hands, the procedure described by Clary and Back 56 (Scheme 1f) afforded E-1 and Z-1 as components in a rather complex mixture of products.…”

“…Previous Syntheses of 1-Cyano-1,3-butadiene (1) a a (a) Carothers and Berchet; 38 Coffman. 39 (b) Snyder et al 41 (c) Daessle et al 48 (d) Katagiri et al 53 (e) Braun et al 55 (f) Clary and Back. 56 (g) Banert.…”

Evidence for Competing syn and anti Pathways in Palladium-Catalyzed Eliminations of Acyclic Allylic Carbonates

“…[15] In this context, the idea came up to use carbonates derived from diastereomeric aldols as a suitable probe for the elucidation of the stereochemical outcome in palladium-catalyzed eliminations. For this purpose, lithium enolates derived from 2',4',6'-trimethylpropiophenone 5 were added to (E)-crotonaldehyde, and the lithium alkoxide formed thereby was converted in situ into the diastereomeric carbonates 6 a and 6 b upon treatment with methyl chloroformate (Scheme 2).…”

Atropisomeric benzamides and naphthamides as chiral auxiliaries †

“…The anti-selective aldol reactions of hindered aryl esters appear as key steps in synthetic routes to davanone, 23 lankanolide, 24 the pamamycins, 25 erythronolides A 26 and B 27 and the vitamin E side chain, 28 among others. 29,30 Scheme 1 anti-Aldol reactions with hindered phenyl esters.…”

Synthesis and Characterization of Cyanobutadiene Isomers—Molecules of Astrochemical Significance

“…Rather, the sensitivity of 1 to undergo reaction (dimerization, polymerization) or degradation (heat, light, strong bases, and silica/alumina gels) greatly complicates the task of purifying and characterizing 1. Our attempts to replicate the procedure reported by Braun et al 55 (Scheme 1e) failed to produce an isolable amount of the expected mixture of diastereomers. In our hands, the procedure described by Clary and Back 56 (Scheme 1f) afforded E-1 and Z-1 as components in a rather complex mixture of products.…”

“…Previous Syntheses of 1-Cyano-1,3-butadiene (1) a a (a) Carothers and Berchet; 38 Coffman. 39 (b) Snyder et al 41 (c) Daessle et al 48 (d) Katagiri et al 53 (e) Braun et al 55 (f) Clary and Back. 56 (g) Banert.…”

Evidence for Competing syn and anti Pathways in Palladium-Catalyzed Eliminations of Acyclic Allylic Carbonates

“…[15] In this context, the idea came up to use carbonates derived from diastereomeric aldols as a suitable probe for the elucidation of the stereochemical outcome in palladium-catalyzed eliminations. For this purpose, lithium enolates derived from 2',4',6'-trimethylpropiophenone 5 were added to (E)-crotonaldehyde, and the lithium alkoxide formed thereby was converted in situ into the diastereomeric carbonates 6 a and 6 b upon treatment with methyl chloroformate (Scheme 2).…”

Atropisomeric benzamides and naphthamides as chiral auxiliaries †

“…The anti-selective aldol reactions of hindered aryl esters appear as key steps in synthetic routes to davanone, 23 lankanolide, 24 the pamamycins, 25 erythronolides A 26 and B 27 and the vitamin E side chain, 28 among others. 29,30 Scheme 1 anti-Aldol reactions with hindered phenyl esters.…”