Heck-type vinylation

Heck type vinylation of 4-bromo-l-(4-methylphenylsulfonyl)-indole proceeds in good yield with such alkenes as methyl acrylate, styrene and N-vinylphthalimide using Pd(OAc)2 (5 mol%) and tri-o-tolylphosphine as the... 

Fig. 21. Heck-type vinylation reaction with PolyHIPE-supported Pd catalyst...

The equivalent intramolecular Heck-type vinylation of a a>-vinyl-(Z)-iodoalkene has been used as the key step in the synthesis of A-ring synthons for 1 at,25-di hydroxy vitamin D3 and its analogues403. The reaction takes place under reflux in acetonitrile in the presence of one equivalent of triethylamine404 and gives a 81% yield (equation 102). 

Heck-type vinylations of alkynic halides proceed only under solid-liquid phase-transfer conditions. These mild conditions allow the reaction to be performed with thermily unstable substrates. Thus, methyl ( )-enynoates can be obtained from the reaction of 1-iodoalkynes with methyl 2-propenoate in DMF at room temperature in the presence of potassium carbonate, tetrabutylammonium chloride and a catalytic amount of palladium acetate (Scheme 36)." ... 

Palladium phosphines served as improved catalysts for additions across the C-C bond of biphenylene. Olefins could be incorporated by a Heck-type vinylation, presumably involving insertion into the aryl-Pd bond of a biphenylyl metallacycle followed by P-elimination and reductive elimination of product (9). Suzuki-type additions could be made using arylboronic acids (10). It was also found that weakly acidic C-H bonds could serve as addition partners, such as methyl ketones or benzylic nitriles (11, 12) [21]. In these reactions, Pd(0) was proposed to insert first into the biphenylene C-C bond generating L2Pd(2,2 -biphenylyl), which was then protonated by p-cresol to leave a Pd-aryl bond that went on to couple with the conjugate base of the substrate to give the product. 

A similar approach was used by the Alcaide group [183] in the synthesis of tricyclic (3-lactams 6/1-391 from 6/1-390 (Scheme 6/1.99). In this domino process the primarily obtained it-allyl-Pd-complex reacts with the N-nucleophile of the urethane moiety to form a C-N-bond and a vinyl halide. The final step is then an intramolecular Heck-type reaction of the vinyl halide with the alkyne moiety and re-... 

Reaction of organic halides with alkenes catalyzed by palladium compounds (Heck-type reaction) is known to be a useful method for carbon-carbon bond formation at unsubstituted vinyl positions. The first report on the application of microwave methodology to this type of reaction was published by Hallberg et al. in 1996 [86], Recently, the palladium catalyzed Heck coupling reaction induced by microwave irradiation was reported under solventless liquid-liquid phase-transfer catalytic conditions in the presence of potassium carbonate and a small amount of [Pd(PPh3)2Cl2]-TBAB as a catalyst [87]. The arylation of alkenes with aryl iodides proceeded smoothly to afford exclusively trans product in high yields (86-93%) (Eq. 61). 

Suitably positioned vinyl halide can undergo Heck-type intramolecular coupling to generate dienes (equations 124 and 125)216,217. When one of the reacting partners in the Heck reaction is a diene, trienes are obtained (equation 126)218. Heck coupling of ally lie alcohols and alkenyl iodides has been employed for the synthesis of vitamin A and related compounds (equation 127)219,220. A similar double Heck reaction on a Cio-diiodide with a Cis-allylic alcohol leads to -carotene as a mixture of isomers (equation 128)209e. 

Following our first report on the palladium-catalyzed reaction of vinyl triflates with olefins (Heck-type reaction), oxidative insertion of palladium(O) into the carbon-oxygen bond of easily available vinyl triflates ... 

Palladium-catalyzed coupling reactions of the Heck type have in many instances involved indole and pyrrole derivatives. Although the mechanisms are complex, organopalladium species are implicated (84H(22)1493). Vinylation of A-substituted-3 -iodoindoles with amidoacrylate groups provides a useful functionalization of indoles (Scheme 81) (90JOM(39l)C23). Yields are improved in intramolecular reactions, e.g. (406 — 407) and (408 — 409) <92H(34)219,91CPB2830). 

Aryl cyanides add to norbornene and norbornadiene under nickel catalysis to give (2/U,35 )-3-aryl-2-cyanobicyclo[2.2.11heptanes and (2/U,3.S )-3-aryl-2-cyanobicy-clo[2.2.1]hept-5-enes in good yields with a broad substrate scope. On the other hand, the reaction of an aryl cyanide with triethoxy(vinyl)silane gives a Heck-type arylation product, suggesting the arylnickelation pathway in the catalytic cycle.68... 

The Heck-type reaction of vinylic bromides with alkenes in the presence of nucleophiles such as stabilized enolates or secondary amines (morpholine or piperidine) are efficient three-component reactions that were developed in the late 1970s... 

The Heck-type reaction. The Heck reaction135 (or some modified procedure of it) is certainly one of the most powerful tools used in the preparation of precursors with acetylenic and vinylic subunits. For instance, in the case of precursors 46-49 the synthesis is conveniently achieved by a cross-coupling reaction in the presence of palladium complexes as catalyst. Two pathways are possible, as represented by equations 9 and 10108. 

With a combination of organic halide, alkene or alkyne, and palladium catalyst, the reaction may take a superficially similar, but different pathway other than a Heck-type reaction. In these, the halogen is retained in the products, as an alkyl or vinyl halide. These results occur when the starting organic halide is allyl, a- to a carbonyl or similar group, or attached to a perhalogenated carbon atom. In much of the early work, mixtures with Hecklike elimination products were obtained, due to elimination caused by the presence of amine bases in the reaction mixture (equation 165)323. 

Ruthenium(O) complexes such as Ru(COD)(COT) catalyze the dehydrohalo-genative coupling of vinyl halides with olefins to give substituted conjugated dienes in a Heck-type reaction [11]. Thus, alkenyl halides readily react with activated olefins to produce dienes 16 (Eq. 7). Oxidative addition of vinyl halide, followed by regioselective insertion of an electron-deficient olefin and by -hydrogen elimination leads to the diene. 

There are scattering examples that neutral organosilanes R-SiMe3 undergo a desilylative coupling reaction with aryl halides in the presence of a palladium catalyst. Hallberg and his co-workers disclosed that trimethyl(vinyl)silane reacts with an arylpalladium(II) complex to afford coupled products accompanied by aryl-substituted alkenylsilanes formed through the Heck type reaction... 

Suitably positioned vinyl halide can undergo Heck-type intramolecular coupling to generate dienes (equations l24 and When one of the reacting partners in the... 

Hiyama and Mori introduced the Mizoroki-Heck-type reaction of aryl- and vinyl-... 

Here, the term Heck-type reaction summarizes palladium-catalyzed C—C coupling processes where vinyl or aryl derivatives are functionalized with alkenes, al-kynes, or organometallic reagents (see Eqs. 1 and 2) [1], Aryl and vinyl chlorides are most reluctant to undergo Pd-catalyzed activation, as expected from C—X bond... 

Various examples of intramolecular stereoselective carboamination have been reported28 "30. Asymmetric synthesis of key intermediates for capnellenols is achieved via a Heck-type intramolecular carbopalladation of an alkene with a vinyl halide and amide anion capture in the presence of Chiraphos- or BINAP-modified palladium catalysts31. 

Heck-type coupling of allylic alcohols and enol triflates.- This vinylation of allylic alcohols can be effected by catalysis with Pd(OAc)2 and tri-o-tolylphosphine (1 2) and triethylamine (excess) as base. The major products arc conjugated dicnols. 

Heck-type reaction. Aryl and vinylic mercurials undergo coupling reactions with -alkenyl-/3-lactams in the presence of PdCU, CuCU, and LiCl. Ring opening with double bond migration occurs during the reaction. 

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