Experimental and theoretical studies evidence an unconventional biradical character for the titanium enolates derived from α-alkoxy ketones and TiCl4. EPR experiments and ab initio calculations suggest that these titanium enolates have an open shell electronic ground state.

Alternative titanium-mediated aldol procedures based on several protected beta-hydroxy ethyl ketones have been surveyed. Eventually, enolization of (S)-1-benzyloxy-2-methyl-3-pentanone (1) with (i-PrO)TiCl3/i-Pr2NEt provided a very reactive enolate that afforded the corresponding 2,4-syn-4,5-syn aldol adducts in high yields and diastereomeric ratios with a broad range of aldehydes.

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