Enynes/dienynes, cycloaddition

Further research on this subject was recently reported, in relation to the use of dienynes as substrates for intramolecular cycloaddition. While thermal intramolecular [4+2] cycloadditions of enynes with alkenes only took place at high temperatures, the gold(I) catalyzed transformations provided bi- or tri-cyclic ring systems under mild conditions [152]. 

P Volume 1,1991,283 pp. 109.50/ 69.50 ISBN 1-55938-180-9 CONTENTS Introduction to the Series An Editor s Foreword, Albert Padwa. Preface, Brian Halton. Strain in Organic Chemistry A Perspective, Brian Halton. Gem-Dihalocyclopropanes in Chemical Synthesis, Martin G. Banwell and Monica E. Re-um. 1-Halo- and 1, 2-Dihalocyclopropenes Useful Synthetic Intermediates, Mark S. Baird. Cyciization and Cycloaddition Reactions of Cyclopropenes, Albert Padwa and Glen E. Fryx-ell. New Synthetic Pathways From Cyclobutanones, Edward Lee-Ruff. Cyclic Alkynes, Enynes and Dienynes A Synthetic Challenge, Herbert Meier. Index. 

A more complex mechanism via enyne cyclization and metathesis followed by metalladiene cycloaddition is discussed in the formation of bicyclo[3.1.0]hexanes from dienynes and dienes in the presence of a palladacyclopentadiene catalyst. ... 

Similarly, enynes substituted at the alkyne with an aryl group led to products resulting from a formal intramolecular [4 + 2] cycloaddition occurring at an unusual low temperature (equation 64). On the other hand, substrates with = H or = Me, R = H gave cyclobutenes with Au(i)25,34 qj. catalysts. Dienynes react with cationic Au(I) catalysts leading to products of formal [4 + 2] cycloaddition as well (equation 65). Somewhat related cyclizations of allenes with alkynes and diynes have been described. 

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