Acetoxypalladation of alkyne

PALLADIUM(II)-CATALYSED CYCLIZATION OF ALKYNES WITH ALDEHYDES, KETONES OR NITRILES INITIATED BY ACETOXYPALLADATION OF ALKYNES... 

The reaction type (a) (L = OAc) in Scheme 15 takes place in the palladium-catalyzed reaction of the alkyne-allyl acetates 57 with acetic acid the trans-acetoxypalladation of alkyne leads to 59, and subsequent carbopalladation of alkene followed by deace-toxypalladation gives the five-membered heterocycles 2-alkenylidenelactones 58 (Scheme 20).101a... 

The same gronp [156] applied this protonolysis approach to an inter- and intramolec-nlar enyne conpling that starts with an acetoxypalladation of alkynes followed by cy-clization to yield a wide variety of carbo- and heterocyclic componnds. Moreover, the... 

Zhao, L., Lu, X. and Xu, W. (2005) Palladium(n)-catalyzed enyne couphng reaction initiated by acetoxypalladation of alkynes and quenched by protonolysis of the carbon-paUadium bond. J. Org. Chem., 70, 4059-63. 

The synthesis of five-membered carbo- and hetero-cyclic compounds, including fused rings, has been reported using acetate as a nucleophile in the cyclization of 1,6-enynes under palladium(II) catalysis (Scheme 91). The reaction is initiated by trans-acetoxypalladation of the alkynes and quenched by either trans- or ra-deaceloxypal-ladation in the presence of 2,2/-bipyridine as the ligand.134... 

E)- and (ZyAlkenes. Alkenylboranes (1), prepared by hydroboration of 1-alkynes, are converted into (E)-alkenes (2) by reaction with palladium(II) acetate (1 equiv.) and triethylamine (0.7-1.0 equiv.). The reaction is believed to involve c/s-acetoxypalladation, 4higration with inversion of R from boron to carbon, and cis i9-elimination (equation I). ... 

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