Alkyne arylation

The utility of the stepwise, double-coupling procedure is demonstrated in the parallel synthesis of Tamoxifen derivatives on solid support [127] (Scheme 1-29). 1-Alkenylboronates thus obtained by a diboration-cross coupling sequence are further coupled with p-silyUodobenzene supported on polymer resin. Using this strategy, each position about the ethylene core is modified by the appropriate choice of alkyne, aryl halide, and cleavage conditions for the synthesis of a library of Tamoxifen derivatives. 

Relevant complexes have been isolated and fully characterized (4-10, 13-lb). The resulting arylpalladium complex 8 is able to react with various compounds such as terminal alkenes, alkynes, aryl boronic acids or hydrogen-transfer agents to give an organic molecule and palladium(O) (3, 17, 18). 

Diels-Alder reactions. The reagent undergoes [4-i-2]cycloadditions to give adducts bearing an alkenylstannane moiety. Accordingly, it can be considered as a synthetic equivalent for acetylene and substituted alkynes (aryl, acyl, and haloalkynes). 

Generally, arene(alkoxy)carbene chromium complexes react with aryl-, alkyl-, terminal or internal alkynes in ethers or acetonitrile to yield 4-alkoxy-l-naphthols, with the more hindered substituent ortho to the hydroxyl group . Upon treatment with alkynes, aryl(dialkylamino)carbene chromium complexes do not yield aminonaphthols, but they form indene derivatives . Vinyl(dialkylamino)carbene complexes, however, react with alkynes to yield aminophenols as the main products The solvent is one of the many factors that affects this type of reaction, for which the most important is the polarity and/or coordinating ability of the solvent. The Dotz benzannulation reaction yields either arene chromium tricarbonyl complexes or the decomplexed phenols, depending on the work-up conditions. Oxidative work-up yields either decomplexed phenols or the corresponding quinones. 

Disubstituted benzoic esters arise from an Ir-catalyzed [2+2+2]cycloaddition involving propynoic esters and two equivalents of 1-alkynes. Aryl eth3myl suUdnes also react similarly. ... 

Alkene-,alkyne-,aryl-phosphonic and phosphinic acids.-(of-Stannylalkyl)phosphonic acid diesters have been employed to prepare alkenylphosphonic diesters. Treatment of the tin compounds (251) (generated in situ) with an aldehyde R CHO at -70 yielded a mixture of ( ) and (Z) isomers of (252), the proportions being controlled essentially by... 

Up to now, the cycloadditions of chromium coordinated alkynes, aryl (vinyl) carbenes and carbon monoxide has received the widest attention. This route provide a straightforward entry into hydroquinoid and quinoid structures which represent key elements in many natural products. 

From To - Alkanes Cycloalkanes Alkenes Alkynes Aryls Halogen compounds Alcohols Phenols Ethers, Quinones B. and Si compounds P and 6i compounds Nitro, Nitroso, Azo, Azoxy, Hydrazo, ides Amines Organometallic Aldehydes Ketones Acids, Anhydrides, Esters Arn.des, Amidines, Nitriles Hydroky-aldehydes Amino Heterocycles Nucleosides Miscellaneous, including heterocycles... 

The high regio- and stereoselectivities of the process as well as its tolerance of functional groups underline the potential of the methodology. Its wide synthetic applicability is demonstrated by the preparation of a variety of functionalized heterocycles from readily available alkynes. Aryl and alkenyl halides or triflates, alkynyl halides, allyl and... 

Figure 1.30 A cross-section of products successfully prepared by the Pd-catalyzed alkyne arylation by William s laboratory [108],...

Figure 4.46 A cross-section of results for the Pd-catalyzed direct C-H bond alkyne arylation as by Ackermann and coworkers [90b].

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