Tetrabutylammonium triphenyldifluorosilicate (TBAT)

Nucleophilic fluorination of primary alkyl halides 4 and 5, secondary alkyl halides, tosylate 6, mesylates and triflate 8 has been achieved using TBAT as a fluoride source. These reactions produced alkyl fluorides in good yields with minimal contamination from alkene or alcohol byproducts. 1 (Chemical Equation Presented) Tetrabutylammonium triphenyldifluorosilicate (TBAT) has been employed as a fluoride source to generate in situ carbanions from organosilanes 10, 13 and 15; these anions have been reacted with a number of electrophiles including imine 16, aldehyde 11 and ketones, in moderate to high yields. Tetrabutylammonium triphenyldifluorosilicate (TBAT) can be used in catalytic quantities in the reaction of organosilane compounds with aldehydes. 2 (Chemical Equation Presented) The allylfluorosilicate species produced by reaction of TBAT with allyl silanes have been reacted with N-acylhydrazones 18 in the presence of indium(III) trifluoromethanesulfonate to produce allyl adducts 20 with good diastereoselectivity. Tetrabutylammonium triphenyldifluorosilicate (TBAT) is unique in this role as a fluoride source since it is the only fluoride source which is compatible with activation of the electrophile (18) with a Lewis acid.3,4 (Chemical Equation Presented) A route to multisubstituted indolizidines 22 has been developed, the key step involving the fluoride ion induced intramolecular reaction of 2,3-dihydro-4-pyridinones 21 with a pendant allylsilane. Tetrabutylammonium triphenyldifluorosilicate (TBAT) was found to be the most effective fluoride source in these reactions, leading to the highest yields and minimal side products.6 (Chemical Equation Presented) The diastereoselective Michael addition of lactone 23 to the enone system 27 has been carried out using TBAT as a fluoride source. The formation of trimethylsilyl enol ether 24 was achieved by the reaction of lactone 23 with a-trimethylsilyl ester 26 in the presence of catalytic TBAT. Activation of this intermediate 24 (also with TBAT) and reaction with enone 27 produced ketone 25 diastereoselectively in good yield in a single reaction pot.7 (Chemical Equation Presented) It has been established that hypervalent silicate compounds can undergo Pd(0)-catalysed cross-coupling reactions and are a viable alternative to toxic stannanes or boronic acid derivatives which can be difficult to prepare. Tetrabutylammonium triphenyldifluorosilicate (TBAT) has proved to be a good phenyl source in Pd(0)-catalysed cross-coupling reactions with allylic ester 28,8 aryl halides 3110 and aryl triflates 32.10 (Chemical Equation Presented) © Georg Thieme Verlag Stuttgart.