B. Feringa, W. Jager, B. D. Lange
May 12, 1992
Citations
0
Influential Citations
43
Citations
Journal
Tetrahedron Letters
Abstract
The synthesis and resolution of 2-methyl-9H-thioxanthene-9-(9H-thioxanthen-9-ylidene) 1 and related structures 2-5, being the first examples of thermally stable optically active sterically overcrowded ethylenes, are reported. Substitution of the sulfur atom in the thioxanthene part of 1 with an X group (2, X = C(CH3)2; 3, NCH3; 4, O) results in a change in racemization barrier (1, 27.4 kcal.mol-1; 2, 25.1 kcal.mol-1; 3, 21.3 kcal.mol-1; 4, <20 kcal.mol-1) depending upon the aryl-X bond lenghts.