Halides palladium-catalyzed reaction with alkenyl

Most of the work on the C-N bond-forming crosscoupling reactions has concentrated on the formation of aromatic C-N bonds. Recent studies show that the application of cross-coupling reactions to alkenyl halides or triflates furnished enamines (Scheme 19) (for palladium-catalyzed reaction, see 28,28a-28d, and for copper-catalyzed reaction, see 28e-28g). Brookhart et al. studied the palladium-catalyzed amination of 2-triflatotropone 109 for the synthesis of 2-anilinotropone 110.28 It was found that the reaction of 109 proceeded effectively in the presence of racemic BINAP and a base. As a simple method for the synthesis of enamines, the palladium-catalyzed reactions of alkenyl bromide 111 with secondary amine were achieved under similar conditions.2841 The water-sensitive enamine 112 was isolated as pure compound after dilution with hexane and filtration through Celite. The intramolecular cyclization of /3-lactam 113, having a vinyl bromide moiety, was investigated by Mori s... 

The palladium-catalyzed reaction of alkenyl-, aryl-, alkynyl- and alkylsiloxanes with aryl, alkyl, and alkenyl halides and triflates in the presence of activators is known as the Hiyama cross-coupling reaction and several reviews have been published. This chapter will present major developments and examples of recent carbon-carbon bond formation methodology and improvements as well as their use in natural products synthesis in the last few years. 

Organozinc compounds are also useful in palladium-catalyzed coupling with aryl and alkenyl halides. Procedures for arylzinc,156 alkenylzinc,157 and alkylzinc158 reagents have been developed. The ferrocenyldiphosphine dppf has been found to be an especially good Pd ligand for these reactions.159... 

A unique system for catalytic silaboration of allenes, in which a catalytic amount of organic halide is used as a crucial additive, has been reported (Equation (86)).232 In the presence of Pd2(dba)3 (5 mol%) with 3-iodo-2-methyl-2-cyclohexen-l-one (10mol%), reactions of terminal allenes with a silylborane afford /3-silylallylboranes in good yields with excellent regioselectivity. It is worth noting that the addition takes place at the terminal C=C bond in contrast to the above-mentioned palladium-catalyzed silaboration. The alkenyl iodide can be replaced with iodine or trimethylsilyl iodide. The key reaction intermediate seems to be silylpalladium(n) iodide, which promotes the insertion of allenes with Si-C bond formation at the central -carbon. 

The reaction of heterocyclic lithium derivatives with organic halides to form a C-C bond has been discussed in Section 3.3.3.8.2. This cannot, however, be extended to aryl, alkenyl or heteroaryl halides in which the halogen is attached to an sp2 carbon. Such cross-coupling can be successfully achieved by nickel or palladium-catalyzed reaction of the unsaturated organohalide with a suitable heterocyclic metal derivative. The metal is usually zinc, magnesium, boron or tin occasionally lithium, mercury, copper, and silicon derivatives of thiophene have also found application in such reactions. In addition to this type, the Pd-catalyzed reaction of halogenated heterocycles with suitable alkenes and alkynes, usually referred to as the Heck reaction, is also discussed in this section. 

Transition metal-catalyzed cross-coupling reactions between vinyl organometallic compounds and unactivated alkyl halides that can be usually performed with palladium, nickel and cobalt are of particular synthetic interest [37-39]. Recently, the groups of Cahiez [48] and Cossy [49] concurrently reported the first iron-catalyzed reaction of alkenyl Grignard compounds with primary and secondary alkyl halides (X=Br, I) (Scheme 5.15). The two protocols basically differ in the iron source... 

Organoboranes react with propargylic carbonates. Usually, addition of a base is indispensable for the palladium-catalyzed reactions of organoboranes with aryl, alkenyl, and allyl halides. But the reaction of organoboranes with methyl propargyl carbonates proceeds... 

The nickel- or palladium-catalyzed reaction of stereodefined alkenyl halides with trimethylsilylmethylmagnesium chloride (TMSCH2MgCl) delivers allylsilanes with excellent regio- and stereocontrol. 

Miyaura, N., Yamada, K., Suzuki, A. A new stereospecific cross-coupling by the palladium-catalyzed reaction of 1-alkenylboranes with 1-alkenyl or 1-alkynyl halides. Tetrahedron Lett. 1979, 3437-3440. 

Hayashi S, Yorimitsu H, Oshima K (2009) Synthesis of aziridines by palladium-catalyzed reactions of allylamines with aryl and alkenyl halides evidence of a syn-carboamination pathway. Angew Chem 48 7224-7226. doi 10.1002/anie.200903178... 

Sample Solution (a) Palladium-catalyzed reactions of organozinc compounds with alkenyl halides give cross-coupling in which bond formation occurs between the carbon attached to zinc and the carbon attached to the halogen. The stereochemistry at the double bond of the iodoalkene is retained. The product is (f)-6-methyl-l,5-decadiene. 

Alkenylsilanols or isopropoxysilanes have been recently used for cross-coupling reactions of aryl or alkenyl halides under mild conditions. The palladium-catalyzed reaction of silanols has been optimized in the presence of Pd(dba)2, but in some cases the use of dimer (1) gave better results.The reaction of (Z)-vinylsilanols with vinyl iodides led to (Z,Z)-diene derivatives in 68% yield (eq 84). The stereoselectivity of the reaction was found to he 92.4% in favor of the (Z,Z)-isomer. 

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