Emergencies boron trifluoride

In addition to the boron trifluoride-diethyl ether complex, chlorotrimcthylsilanc also shows a rate accelerating effect on cuprate addition reactions this effect emerges only if tetrahydrofuran is used as the reaction solvent. No significant difference in rate and diastereoselectivity is observed in diethyl ether as reaction solvent when addition of the cuprate, prepared from butyllithium and copper(I) bromide-dimethylsulfide complex, is performed in the presence or absence of chlorotrimethylsilane17. If, however, the reaction is performed in tetrahydrofuran, the reaction rate is accelerated in the presence of chlorotrimethylsilane and the diastereofacial selectivity increases to a ratio of 88 12 17. In contrast to the reaction in diethyl ether, the O-silylated product is predominantly formed in tetrahydrofuran. The alcohol product is only formed to a low extent and showed a diastereomeric ratio of 55 45, which is similar to the result obtained in the absence of chlorotrimethylsilane. This discrepancy indicates that the selective pathway leading to the O-silylated product is totally different and several times faster than the unselective pathway" which leads to the unsilylated alcohol adduct. A slight further increase in the Cram selectivity was achieved when 18-crown-6 was used in order to increase the steric bulk of the reagent. 

Conjugate additions of alkylcopper- boron trifluoride to enoates of sulfonamide-shielded alcohols (6 and 7) quite generally proceeded with >99% de and >90% yield30. The following general trend has emerged from the reactions of 6 and 7. 

In the event of accidental release of boron trifluoride gas, evacuate the area, and if the cause of the release is a leaking cylinder, remove the cylinder to a fume hood or open area if it is possible to do so safely. Positive pressure air-supplied respiratory protection and protective elothing may be necessary to deal with a leaking cylinder of boron trifluoride, and emergency response personnel should be notified. 

Leaks can readily be detected by the dense white fumes formed by boron trifluoride in moist air or by its sharp and irritating odor. Emergency personnel equipped with complete breathing, eye, and skin protective equipment are the only ones who should respond to correct leaks others should leave the area at once until the leak(s) have been stopped and the area has been thoroughly purged of vapors and secured. Emergency procedures for dealing with leaks should be fully established and practiced in advance. 

Fully encapsulating (Level A) suits with an SCBA must be available for emergencies that may make it necessary for personnel to enter an area containing a high concentration of boron trifluoride. 

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