Heck reaction rearrangement

Dihydroxy-l,3-dioxepins readily undergo vinylacetal rearrangement in the presence of a Lewis acid to give tetrahydrofuran-3-carbaldehydes (CHEC-II(1996)). This methodology was applied in a tandem Heck reaction -rearrangement process for the synthesis of a variety of 2,4-substituted tetrahydrofuran-3-carbaldehydes (Scheme 19) <2006CC3119>. 

A chelation-assisted Pd-catalyzed Cope rearrangement was proposed in the reaction of phenanthroline to generate isoquinolinone derivatives (Eq. 12.78).177 The use of aqueous media and ligands enables a double-Heck reaction on a substrate favoring alkene insertion over (J>-hydride elimination. 

Triflates also undergo Heck reactions and Gribble and Conway reported several such couplings of l-(phenylsulfonyl)indol-3-yl triflate (34) to afford 3-vinylindoles 224 [183]. Cyclohexene, allyl bromide, and methyl propiolate failed to react under these conditions, but triphenylphosphine afforded 225 in excellent yield (93%), and divinyl carbinol yielded the rearranged enal 226 (82% yield). 

Mdrour also explored the Heck reactions of indolyl triflates with allylic alcohols [139, 258]. For example, reaction of triflate 227 with allyl alcohol gives the rearranged allylic alcohol 228 [139],... 

Keywords Alkynyl lactams, Heck reaction, Domino-Heck type reaction, rearrangement... 

Aromatic substitution 21 Baeyer-Villiger 20 Beckmann rearrangement 20 Henry reaction 21 Friedel-Crafts21 Heck reaction 21 Osmylation 89... 

A ir,o domino-Heck reaction under concomitant rearrangement of the tetracyclic allylcyclopropane endo,exo-bishomobarrelene has been reported 138 the stereoselective reaction proceeds via an intramolecular insertion of a primarily formed carbopallada-tion intermediate into a strained cyclopropane C-C cr-bond (Scheme 96). 

The key intermediate in the total synthesis of furaquinocin was obtained in good yield by a reductive Heck reaction that proceeded with a sterically hindered base pentamethylpiperidine (PMP) <02JA11616>. A new hypothesis for the major skeletal rearrangement (anthraquinone —> xanthone —> coumarin) that occurs in the complex biosynthesis of aflatoxin Bi was proposed. To test this hypothesis, an intermediate 11-hydroxy-O-methylstergmatocystin (HOMST) was synthesized as shown below. The key transformation in this synthesis involved the treatment of an ester-aldehyde with Pr3SiOTf, which smoothly produced a mixed acetal. Direct reduction with DIBAL-H led to the aldehyde. The desired product was eventually obtained via several steps as shown <02JA5294>. 

Scheme 32 Sequential Claisen rearrangement-intramolecular Heck reaction [84]...

Vinylation of heteroaryl triflates also possible. Vinyl halides can be coupled to alkenes to form dienes. " The reaction of dihydrofurans with vinyl triilates and a palladium catalyst leads to a nonconjugated diene, 33. This example illustrates that the product is formed by an elimination step, as with the Heck reaction (13-10), and double bond migration can occur resulting in allylic rearrangement. 

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