02073nas a2200265   4500008004100000022001400041245015100055210006900206260010600275300001400381490000700395520103400402653001301436653003001449653002601479653002401505100001901529700002001548700001301568700001901581700002501600700002501625700002601650856013101676       2006                        eng d  a0040-402000a[6+3] cycloaddition of pentafulvenes with 3-oxidopyrylium betaine: a novel methodology toward the synthesis of 5-8 fused oxabridged cyclooctanoids0 a63 cycloaddition of pentafulvenes with 3oxidopyrylium betaine a   aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcJUN  a5952-59610 v623 a<p>Pentafulvenes undergo a facile [6+3] cycloaddition with 3-oxidopyrylium betaine, generated from the corresponding pyranulose acetate, leading to the formation of 5-8 fused oxabridged cyclooctanoids. The product is formed by a [6+3] cycloaddition, followed by a 1,5-hydrogen shift of the initially formed [6+3] adduct. The reaction was found to be general and a number of fulvenes with a wide range of substituents at the exocyclic double bond, that is, at the C6 position followed a similar reactivity pattern. The [6+3] adduct, a 5-8 fused oxabridged cyclooctanoid, is potentially amenable to a number of synthetic transformations due to the presence of an alpha, beta-unsaturated ketone and cyclopentadiene part. By selecting appropriately substituted fulvene and pyranulose acetates, it is possible to use this methodology for the synthesis of a wide range of 5-8 fused cyclooctanoids. The experimental results have been rationalized on the basis of theoretical calculations. (c) 2006 Elsevier Ltd. All rights reserved.</p>10afulvenes10aoxabridged cyclooctanoids10aoxidopyrylium betaine10a[6+3] cycloaddition1 aKrishnan, Syam1 aSajisha, V., S.1 aAnas, S.1 aSuresh, C., H.1 aBhadbhade, Mohan, M.1 aBhosekar, Gaurav, V.1 aRadhakrishnan, K., V.  uhttps://library.ncl.res.in/content/63-cycloaddition-pentafulvenes-3-oxidopyrylium-betaine-novel-methodology-toward-synthesis-1