Titanium ditriflate

The chiral titanium complexes modified by the perchlorate or trifluoromethanesulfonate ligand such as (R)-l,l -bi-2,2 -naphthotitanium diperchlorate (BIN0L-Ti(C104)2) or (7 )-l,l -bi-2,2 -naphthotitanium ditriflate ((I )-BINOL-Ti(OTf)2) can easily be prepared by the addition of Silver(I) Perchlorate or Silver(I) Trifluoromethanesulfonate (2 equiv) to BINOL-TiCl2 (eq 2). ... 

A potentially valuable example of a crossed Claisen condensation was described by Tanabe and Mu-kaiyama in 1986. It arose from their earlier work on titanium(IV) ditriflate [dichlorobis(trifluorometh-anesulfonato)titanium(IV)] and triethylamine as a catalytic promoter of the simple Claisen reaction. The reaction was run in the presence of benzaldehyde, added to observe the aldol reaction, but the propionate anion added to the carbonyl group of another ester molecule in preference (equation 11). The same result was observed in a Dieckmann reaction dimethyl adipate, TiCh (OTf) (1.5 equiv.) and triethylamine... 

In the presence of an amino acid-derived boronate (e.g. 2) or a diamine-tin(II), complex,as Lewis acids, optically active aldol products are obtained in good yields (eq 8). In the addition of KSAs to iminies, a diphosphonium ditriflate (eq 9) or an acidic montmorillonite clay has been claimed to give better results than the originally reported Lewis acids (titanium(IV) chloride and trimethylsilyl trifluoromethanesulfonate ). The products of this reaction are valuable intermediates for the synthesis of p-lactams. Two excellent reviews covering this area have recently appeared. ... 

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