T. Engler, M. Letavic, R. Iyengar
Mar 18, 1999
Citations
0
Influential Citations
52
Citations
Journal
Journal of Organic Chemistry
Abstract
Reactions of 2-methoxy-1,4-benzoquinones 2 and 3 with (E)-propenylbenzenes 1 promoted at −78 °C by Ti(IV)−TADDOLates prepared from diol-(+)-4 afford (1R,6R,7R,8R)-8-aryl-3-methoxy-7-methylbicyclo[4.2.0]oct-3-en-2,5-diones 5/8 or (1R,5R,6R,7R)-7-aryl-3-hydroxy-6-methylbicyclo[3.2.1]oct-3-en-2,8-diones 7/10 in good yield and high ee. (2S,3S)-2-Aryl-6-methoxy-3-methyl-2,3-dihydrobenzofuran-5-ols 6/9 are also found, but in slightly lower ee. Cyclobutanes 5/8 cleanly and efficiently rearrange to the dihydrobenzofurans 6/9 without loss of enantiomeric purity upon treatment with the Ti−TADDOLates at higher temperatures. Reactions of (Z)-propenylbenzene 17 and of indene with 2 and 3 give products in moderate enantiomeric purity. Products obtained from reactions of 1-anisylcycloalkenes with 2 differ significantly in yield and enantiomeric purity. In the latter reactions, the ee's of the cyclobutane products are consistently much higher than those of the dihydrobenzofuran products. More significantly, products of d...