The Heck Reaction Applied to 1,3- and 1,2-Unsaturated Derivatives, a Way towards Molecular Complexity

Abstract

This review is an overview of the last ten years’ use of the Mizoroki–Heck coupling applied to 1,2- and 1,3-dienes. Since both these systems form π-allyl palladium intermediates in Pd(0) coupling, they show particular chemical behavior. Many examples of 1,2-dienes Heck reactions are presented. 1,2-Dienes are important substrates because of their high reactivity that makes them useful building blocks for the synthesis of biologically relevant structures.

An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts

“…The major question here is how viable is it to access conjugated dienes from structurally more challenging allenes through a kinetically difficult and stereochemically undistinguished isomerization. It might not seem like a logical approach; however, our justification is that since there are few well established routes for preparing amido-dienes, our allenamide isomerization strategy (for reviews on allenamide chemistry see [ 21 – 23 ], for reports in 2009, 2010 and 2011 see [ 24 – 43 ], for earlier studies on allenamides see [ 44 – 46 ]) can open the door to construct synthetically useful amido-dienes (for a review on the synthesis of enamides see [ 47 ], for reviews on the chemistry of dienamides see [ 48 – 50 ], for reviews on the chemistry of 2-amino or 2-amido-dienes see [ 51 – 52 ]). Problems with the two primary approaches to access amido-dienes [ 47 ] are that acid-mediated condensations suffer from functional group tolerances, and metal-mediated coupling methods (for reviews on Cu-mediated C–N and C–O bond formations see [ 53 – 55 ], for some examples see [ 56 – 58 ]) suffer from limited access as well as the instability of halo-dienes ( Scheme 2 ).…”

Highly Regio- and Stereoselective Catalytic Synthesis of Conjugated Dienes and Polyenes

“…Existing methods, for example, Pd-catalyzed arylation reactions of substituted conjugated dienes, produce mixtures of regio- and stereoisomers and suffer from low yields and narrow scope. 6 Although dienylboronic acids have been explored for dienylation, they are unstable and difficult to prepare. 7 Aromatic sulfinates have been recently introduced as a new class of stable nucleophiles for Pd-catalyzed biaryl couplings.…”

Palladium Catalyzed Stereospecific Arylation of Biocatalytically Derived Cyclic 1,3-Dienes: Chirality Transfer via a Heck-Type Mechanism

“…However, only two products can be formed through a Heck-type mechanism: the observed C-4 arylation product as well as the product 10 (Figure 2) formed from arylation at C-6 followed by palladium migration through a π-allyl system and subsequent β-hydride elimination. 26 The selectivity-determining step in a Heck-reaction is the migratory insertion (carbopalladation). 27 This step generally operates under Curtin-Hammett control 25b, 28 and sometimes follows a Halpern-type selectivity, where the lowest energy transition state arises from a thermodynamically disfavored intermediate.…”