S. Laschat et al., NOVEL (IMINO-ETA(6)-ARENE)CHROMIUM COMPLEXES AND THEIR DIASTEREOSELECTIVE INTRAMOLECULAR HETERO-DIELS-ALDER REACTIONS, Organometallics, 12(9), 1993, pp. 3738-3742
Novel (imino-eta6-arene)chromium complexes 3 with nonactivated olefins
tethered to the 2-azadiene system were prepared and further used in a
new diastereoselective intramolecular Lewis-acid-catalyzed hetero-Die
ls-Alder reaction to give (eta6-octahydroacridine)chromium complexes 4
. The trans selectivity of the cyclization reaction is mainly controll
ed by the Cr-(CO)3 fragment and to a minor extent by the catalyst, sol
vent, and substituents. Complexes 4 also could be obtained by a one-po
t reaction starting from aldehyde 1, (o-toluidine)Cr(CO)3 (2), and Lew
is acid. The stereochemistry of 4a was established by single-crystal X
-ray structure analysis. Compound 4a crystallized in the monoclinic sp
ace group P2(1)/c with a = 9.518(1) angstrom, b = 12.456(1) angstrom,
c = 16.457(1) angstrom, beta = 90.79(1)-degrees, V = 1950.8 angstrom3,
Z = 4, R = 0.038 R(w) = 0.045, and T = 293 K for 343 parameters and 4
426 reflections.