Intramolecular [2+2+2] Cycloaddition Reactions of Yne-ene-yne and Yne-yne-ene Enediynes Catalysed by Rh-I: Experimental and Theoretical Mechanistic Studies

N-Tosyl-linked open-chain yne-ene-yne enediynes 1 and 2 and yne-yne-ene enediynes 3 and 4 have been satisfactorily synthesised. The [2+2+2] cycloaddition process catalysed by the Wilkinson catalyst [RhCl-(PPh3)(3)] was tested with the above-mentioned substrates resulting in the production of high yi...

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Published inChemistry : a European journal Vol. 17; no. 51; pp. 14493 - 14507
Main Authors Dachs, Anna, Pla-Quintana, Anna, Parella, Teodor, Sola, Miquel, Roglans, Anna
Format Journal Article
LanguageEnglish
Published WEINHEIM Wiley 16.12.2011
Subjects
Chemistry
Chemistry, Multidisciplinary
Physical Sciences
Science & Technology
ORGANIC-SYNTHESIS
CARBOCYCLIZATION REACTIONS
CORRELATED MOLECULAR CALCULATIONS
reaction mechanisms
ALKYNES
ENANTIOSELECTIVE CONSTRUCTION
density functional calculations
ALKENES
cycloaddition
PHOSPHINE OXIDES
GAUSSIAN-BASIS SETS
enediynes
rhodium
COBALT
DIYNES
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Summary:N-Tosyl-linked open-chain yne-ene-yne enediynes 1 and 2 and yne-yne-ene enediynes 3 and 4 have been satisfactorily synthesised. The [2+2+2] cycloaddition process catalysed by the Wilkinson catalyst [RhCl-(PPh3)(3)] was tested with the above-mentioned substrates resulting in the production of high yields of the cyclo-adducts. Enediynes 1 and 2 gave standard [2+2+2] cycloaddition reactions whereas enediynes 3 and 4 suffered beta-hydride elimination followed by reductive elimination of the Wilkinson catalyst to give cycloadducts, which are isomers of those that would be obtained by standard [2+2+2] cycloaddition reactions. The different reactivities of these two types of enediyne have been rationalised by density functional theory calculations.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201102210