A highly reactive, low-valent titanium (LVT) reagent has been prepared by the addition of
substoichiometric amounts of iodine to the LVT species generated by Rieke's method (TiCl3−Li−THF). While the conventional McMurry reaction requires high temperatures and prolonged reaction
times for the generation of olefins, the present activated LVT reagent is able to effect the reductive
coupling of aliphatic as well as aromatic carbonyls to the corresponding olefins at lower temperatures
and much reduced reaction times. The protocol is also useful for the intramolecular coupling reactions leading to the one-step synthesis of heterocycles. The temperature-controlled McMurry reaction provides enhanced diastereoselectivity and features an excellent chemoselectivity. In addition
to the McMurry reaction, other SET-induced carbon−heteroatom (O, N) bond cleavages can also
be carried out with the activated reagent at a fast rate and at a low temperature in high yields.
By the promotion of benzotriazole (20 mol %), two molecules of anilines (or other arylamines) and two molecules of phenylacetaldehyde (or o-bromophenylacetaldehyde) condensed to give a series of 1,2,3,4-tetrahydroquinolines in a stereoselective manner. By the catalysis of SmI(2) or SmI(3), the N-(alpha-aminoalkyl)benzotriazoles derived from anilines and (R)-glyceraldehyde acetonide dissociated to the corresponding iminium and enamine species, which underwent asymmetric [4 + 2] cycloadditions to give optically active tetrahydroquinolines.
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