Dialkylboryl trifluoromethanesulfonates

Enolization of ketonic substrates can be carried out under far milder conditions if the dialkylboryl trifluoromethanesulfonate esters 59 (eq. [24]) are employed in the presence of hindered tertiary amines (eq. [43]) (6,63). At low temperatures (-78 0°C),... 

Dialkylboryl trifluoromethanesulfonates, 7, 91-92 9, 131, 140 10, 118 11, 159 Macrolactonization. Trimethylsilyl w-trimethylsilyloxycarboxylates cyclizc to macrolidcs in the presence of 1 equiv. of a dialkylboryl triflate. Dipropylboryl triflate is more effective than diethyl- or dibutylboryl triflate (equation I). 

Direct enolization of carbonyl compounds using dialkylboryl trifluoromethanesulfonate (dialkylboryl triflate R2BOTf) in the presence of a tertiary amine base is versatile and advantageous in many ways compared with the foregoing indirect methods (see Sections 1.7.2.3 and 1.7.2.4).2° The resulting boryl enolates, e.g. (10), react cleanly with various aldehydes to provide high yields of crossed aldol products (Scheme 7). 

B-Bromocatecholborane, 47 Bromodimethylborane, 47 B-Chlorocatecholborane, 47 Chlorotriisopropoxytitanium, 213, 226 Copper(II) bromide, 112 Dialkylboryl trifluoromethane-sulfonates, 340 Dichlorobis( 1 -phenylethoxy)-titanium(IV), 12 Dichlorobis(trifluoromethane-sulfonato)titanium(IV), 102 Dichlorodiisopropoxytitanium(I V), 12 Diethylaluminum chloride, 173 Diethylaluminum fluoride, 25 Dimethylaluminum chloride, 5 Ethylaluminum dichloride, 5, 44, 306 Ferric chloride, 133 Ferric chloride-Silica, 134 Isobutyl(2,4,6-tributylphenoxy)-aluminum trifluoromethanesulfonate, 113... 

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