Low-Valent Titanium Induced Carbonyl Coupling Reactions

OH CH3 OH CH3 1
OH
OH
2
=
=
HO
OH
OH
OH
Ti
Ti
No reaction
3. InterMOLECULAR COUPLING OF ALdEhydES ANd KETONES
3.1 Synthesis of Alkenes
In his effort to develop an alternative process to Wolff-Kishner reaction, McMurry and his
team[7] subjected enone (4) to TiCl 3 /LiAlH 4 and to their surprise, obtained a hydrocarbon, not
the one they anticipated but a reductively dimerized triene (5) in 80% yield.
O
4
CH 3
TiCl 3/LiAlH 4
While McMurry was not alone at the time in making this fundamental discovery[2,3], he was
however, quick to ascertain the potential of his discovery and embarked on exploring the scope
of the new reaction. He soon realised that the reductive coupling reaction was not limited to
α,β-unsaturated ketones but was general for all kinds of ketones and aldehydes and that the
titanium reagent did not isomerize olefin geometry[7].
CH 3
5
3
CH 3
80 %
11