Vinyl halides coupling reactions with

The consecutive reaction of vinyl halides and alkenes with activated methylene systems [42] in the presence of a palladium catalyst and phase-transfer catalyst results from the addition of the methylene carbanion with the initially formed Heck product (Scheme 6.31) an intramolecular version of the reaction leads to the formation of bicycloalk-l-enes (Scheme 6.31) [42], The analogous combined coupling reaction of iodoarenes and activated methylene compounds with non-conjugated dienes under similar conditions forms the monoalkene (Scheme 6.31) [43]. 

The procedure described here Is an example of a general method for preparing conjugated alkadienes by the palladium-catalyzed reaction of 1-alkenylboranes or boronates with vinylic halides. Hydroboratlon of l-a1kynes with catecholborane Is a standard method for obtaining (E)-l-alkenylboronates (1). Several different types of alkenylboranes and boronates (2-4) are now available as reagents for the cross-coupling reaction with vinyl halides. 

The added advantage of the C (1 )-stannylated glycals is their abUity to participate in palladium-catalyzed coupling reactions with organic halides, a process independently reported by Beau [75] and Friesen [81]. Vinyl stannane 237 can be benzylated, allylated or acylated provided that appropriate catalysts are used [75,77] and representative examples are given in Scheme 59. The C-arylation of... 

Organozinc reagents, including the Reformatsky reagents, are extensively used in transition metal catalysed coupling reactions with aryl halides or triflates, vinyl halides, and allylic halides or acetates, as reviewed by Erdik156. Nickel and palladium complexes are... 

Trifluoro-2-propenyl zinc reagent can undergo palladium-catalyzed cross-coupling reaction with aryl or vinyl halides [169,170], which provides a novel method for the introduction of the trifluoromethyl group into organic molecules (Scheme 59). The trifluoro analogue of Naproxen has been prepared by this method [169] (Scheme 60). 

A practical method for preparation of fluorinated alkenyl copper reagents has been recently developed from cuprous halides metathesis of the corresponding zinc or cadmium reagents [180]. These copper reagents exhibit excellent stability at room temperature and undergo a variety of coupling reactions with methyl, allyl, vinyl, aryl and acid halides [180] (Scheme 63). More recently, preparation of cyclic perfluoroalkenyl copper reagents has been reported by the same route [156-158]. 

Stille coupling was also developed in tlie early 1980s and is similar to Suzuki coupling in its sequence. It is used to couple aryl or vinyl halides or triflates with organotin compounds via oxidative addition, transmetallation, and reductive elimination. The oxidative addition reaction has tlie same requirements and preferences as discussed earlier for tlie Heck and Suzuki reactions. The reductive elimination results in formation of tlie new carbon-carbon bond. The main difference is that tlie transmetallation reaction uses an organotin compound and occurs readily without the need for an oxygen base. Aryl, alkenyl, and alkyl stannanes are readily available. Usually only one of tlie groups on tin enters into... 

This coupling of terminal alkynes with aryl or vinyl halides is performed with a palladium catalyst, a copper(I) cocatalyst, and an amine base. Typically, the reaction requires anhydrous and anaerobic conditions, but newer procedures have been developed where these restrictions are not important. 

Acetylenic zinc reagents are readily accessible from 1-alkynes by a deprotonation-transmetallation sequence, and consequently have been successfully used to couple with vinyl halides in many cases (see equation 81), including butadiynyl ones161. Among these, coupling reactions with vinyl bromides have been used in the stereoselective synthesis of enediynes and applied to the synthesis of trienic natural products162. 

In this sense Organ and coworkers [80] have developed intriguing syntheses of polysubstituted olefins based upon consecutive intermolecular reactions such as allylic and allylic-vinylic halide coupling sequences. Therefore, l-acetoxy-4-chloro but-2-ene can be readily submitted as a template for Pd-catalyzed allylic substitutions with two different carbon or nitrogen nucleophiles, leading to unsymmetrically substituted butene derivatives 66-70 in good yields (Scheme 22). Mechanistically, the chloro substituent is replaced... 

Castro et al. 44) found that the order of reactivity of various halides in coupling reactions with ethynylcopper compounds in DMF is ArSX, ArX > RCOX ArCHaX, RCH=CHCH2X, ArCOCHaX > RCH= CHX, Alkyl-X. A somewhat different order is observed for the reactivity of some organic halides towards perhaloarylcopper reagents in THF (97, 147) Allyl Aryl > Alkyl and perfluoroaryl, perfluoro-vinyl > aryl > perfluoroalkyl. Acid halides were also far more reactive than aryl iodides in ethereal solvents 146). The ease of halide displacement is I > Br > Cl. 

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... 

Although trimethyl(vinyl)silane undergoes the coupling reaction with aryl halides in the presence of TASF and a palladium catalyst as described in Section 1 (Eq. 3), those having an aliphatic substituent on vinyl fail to couple with aryl iodides under similar conditions, probably because they are not capable of affording pentacoordinate silicates efficiently owing to the electron-donating nature of the substituent. To assist the formation of the pentacoordinated intermediates, the methyl on silicon was replaced by fluorine [13]. The cou-... 

It has been demonstrated that fluorovinylzinc reagents undergo stereoselective palladium-catalyzed coupling reactions with aryl (e.g., formation of 2 " ), vinyl (e.g., formation of heteroaryl, alkanoyl. and alkoxycarbonyl halides. Fluorovinylzinc reagents also undergo allyl-ation (e.g., formation of 4 ), halogenation, oxidative dimerization, and protonation reactions. ... 

Coupling reactions with vinyl halides are stereospecific. For example, reaction of trans-1 -bromo-1-hexene with (CH3)2CuLi forms rrara-2-heptene as the only stereoisomer (Equation [3]). 

With vinyl halides, coupling is stereospecific. The reaction forms trans alkenes. 

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