Boron inflate

I4 Boron enolates derived from oxazolidinone 3 arc reported to give either syn- or imp-adducts depending on the amounl of boryl Inflate and base employed, the character of the base, and the structure of the aldehyde see H. Danda, M. M. Hansen. C. H. Heathcock, J. Org. Chem. 55,173... 

Dialkylboron trifluoromethanesulfonates (Inflates) are particularly useful reagents for the preparation of boron enolates from carbonyl compounds, including ketones, thioesters and acyloxazoiidinones. Recentiy, the combination of dicylohexyiboron trifluoromethanesulfonate and triethyiamine was found to effect the enolization of carboxyiic esters. The boron-mediated asymmetric aldoi reaction of carboxyiic esters is particuiariy usefui for the construction of anti p-hydroxy-a-melhyl carbonyl units. The present procedure is a siight modification of that reported by Brown, et ai. ... 

Inflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Friedel-Crafts catalysts for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides in the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the Inflates in comparison with the correspond 1 ng fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

The idea that first-row heteroatoms, in the order C 2.5), N 3.1) and 0(3.5), when substituted for B 2.0) might tend increasingly to favor the ni-6 structure seems to be valid, see Figure 8. There also seems to be an even stronger second-row inflation effect in that sulfur, S 2.4), with an electronegativity less than carbon, C 2.5), has an influence half way between N 3.1 and 0(3.5). We would suspect that phosphorous and silicon substitution for boron would have similar second-row inflation effects . 

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