An enantioselective oxidative carbocyclization–borylation of enallenes that is catalyzed by palladium(II) and a Brønsted acid was developed. Biphenol‐type chiral phosphoric acids were superior co‐catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess.
Carbon−Carbon Bond Formation in Regio- and Stereoselective Palladium-Catalyzed Cyclization of Allene-Substituted Conjugated Dienes
作者:Joakim Löfstedt、Johan Franzén、Jan-E. Bäckvall
DOI:10.1021/jo0157324
日期:2001.11.1
Regio- and stereoselective palladium-catalyzed reactions of allene-substituted 1,3-dienes 1 in acetic acid at room temperature lead to cyclization with formation of a carbon-carbon bond between the middle carbon of the allene and the terminal carbon of the 1,3-diene. Two different types of reactions, both that constitute 1,4-carboacetoxylations of the 1,3-diene, have been developed. In one of the reactions
Allenes. Part XI. The preparation of 3-alkyl- and 3,3-dialkyl-1-bromoallenes
作者:S. R. Landor、A. N. Patel、P. F. Whiter、P. M. Greaves
DOI:10.1039/j39660001223
日期:——
3-Alkyl- and 3,3-dialkyl-1-bromoallenes are prepared in excellent yield by the action of hydrobromic acid (45–50%) on secondary or tertiary acetylenic carbinols. They show an exceptionally intense band in the infrared region, a small maximum in the ultraviolet region above 210 mµ, and the expected n.m.r. long range spin–spin coupling.
通过氢溴酸(45%至50%)对仲或叔炔醇的作用,可以以极好的收率制备3-烷基和3,3-二烷基-1-溴代烯丙基。它们在红外区域显示出异常强烈的谱带,在210 m µ以上的紫外区域显示出很小的最大值,并且具有预期的nmr长程自旋-自旋耦合。
Palladium-Catalyzed Oxidative Borylative Carbocyclization of Enallenes
作者:Andreas K. Å. Persson、Tuo Jiang、Magnus T. Johnson、Jan-E. Bäckvall
DOI:10.1002/anie.201008032
日期:2011.6.27
An efficient oxidative carbocyclization/borylation of enallenes uses Pd(OAc)2 as the catalyst, B2pin2 as the boron‐transfer reagent, and 1,4‐benzoquinone (BQ) as the oxidant (see scheme). The reaction seems to take place through activation of the allene by a PdII complex to give an alkenyl–PdII intermediate followed by carbopalladation of the olefin and subsequent cleavage of the intermediate palladium–carbon
Palladium(II)-Catalyzed Oxidative Carbocyclization of Aza-Enallenes
作者:Andreas K. Å. Persson、Jan-E. Bäckvall
DOI:10.1002/anie.201000726
日期:2010.6.21
Live and let diene: A palladium(II)‐catalyzedoxidative carbocyclization reaction of aza‐enallenes provides access to potentially valuable heterocyclic dienes. In the presence of a dieneophile during the carbocyclization step, the products can react further in a one‐pot cyclization/Diels–Alder sequence to give polycyclic products. BQ=para‐benzoquinone.