provided a convenient route for the synthesis of the conjugated yne-allenes 7 or the diastereomeric yne-diallenes, meso-9 and (R,R)/(S,S)-9. Analogously to 7, the phosphorylyne-allenes 14 were also prepared under Stille conditions, starting from the phosphorylallenes 12 and propargylstannane 6a. Alternatively, yne-allenes 17 and 18 were obtained from hexadiynol 16 with orthoester 2b or diethoxychlorophosphane
Cation-Mediated, Substituent-Controlled, C<sup>2</sup>−C<sup>7</sup> Cycloaromatization of an Enyne−Allene
作者:Rolf W. Saalfrank、Martin Haubner、Christian Deutscher、Walter Bauer、Timothy Clark
DOI:10.1021/jo982340x
日期:1999.8.1
Reaction of(2-bromophenylethynyl)trimethylsilane 1 with trimethyl berate yielded the alkynearyl-boronic acid 2, which was coupled in situ with the bromoallenes 3 to give enyne-allenes 4. The intermediates 4 underwent a spontaneous cation-mediated C-2-C-7 cycloaromatization with a concomitant 1,2-shift of the trimethylsilyl group to give the naphthalene derivatives 5. Besides 5, yne-allenes 10 were isolated by chromatography of the crude reaction products. A key step in the formation of 10 is the hydrolysis of the aryl boronic acid 2, which led to phenylethynyltrimethylsilane 8. Under the reaction conditions used, the TMS group of 8 was subsequently removed to give phenylacetylene 9, which further reacted with the bromoallenes 3 to furnish the yne-allenes 10.