Studies in synthesis and stereochemistry
Abstract (Summary)Restricted Item. Print thesis available in the University of Auckland Library or available through Inter-Library Loan. The Lewis and protic acid catalysed dimerization of the 3-methyl-1H-inden-4-ol (3) in non-polar solvents leads to pentacyclic diindeno[7,1-b,c: 2',1'-e]pyrans. The reaction shows kinetic selectivity for the formation of "endo" product (4) while the "exo" dimer (5) is thermodynamically more stable. Under polar conditions, the acid catalysed reaction favours uncyclized diindene (6), while the 1H-indene-l,7-diol (2) affords unstable pentacyclic spiro dimers (29) and (30) merely on standing. When dissolved in trifluoroacetic acid, the dimers derived from indenol (3) dissociate to give the monomeric carbocation (63) which has been identified by n.m.r. spectroscopy. The indenol (14) dimerizes to give four stereoisomeric diindeno[7,1-bc: 2',1'-e]pyrans. Co-dimerization of certain methyl and butyl indenols afforded crossed-dimers which have been isolated by chromatography. Correlation of the n.m.r. spectra of these pentacyclic crossed-dimers with the spectra of dimers derived solely for indenol (3) or (4) allowed unequivocal assignment of most alkyl carbon and proton signals. The relative configuration and stereochemistry of each dimer has been deduced by detailed comparison of n.m.r. spectra and mass spectra. The dimerization of the 4-hydroxy-3-methyl-1H-inden-1-one (35) is less facile than that of the analogous indene (3), but the reaction shows similar kinetic preference for the formation of "endo" dimer (37) which is slightly less thermodynamically stable than "exo" dimer (56). These indenone dimers do not dissociate greatly in trifluoroacetic acid and equilibration is slow. Rapid opening of the pyran ring occurs in base and brief treatment of indenone dimer (37) with hydroxide followed by neutralization afforded the uncyclized diindenone (38).
School Location:New Zealand
Source Type:Master's Thesis
Date of Publication:01/01/1983