Beyond the Balz–Schiemann Reaction: The Utility of Tetrafluoroborates and Boron Trifluoride as Nucleophilic Fluoride Sources

Block‐Structured 1,4‐d‐Glucans by Transglycosidation of Cellulose Ethers

“…They report that oxocarbenium ions formed in carbohydrate transformations can be trapped as glycosyl fluorides, predominantly in the α‐configuration, and these glycosyl fluorides can again act as glycosyl donors. While in the reviewed literature mainly BF 4 − is the fluoride source of such glycosyl fluoride formations, examples for BF 3 , probably from in situ generated fluoroborates R‐O‐BF 3 − , have also been reported . Applied to the cross reaction of two cellulose ether chains, reversible trapping of the oxocarbenium ion as glycosyl fluorides with fluoride from dissociation of the fluoroborate cannot be excluded …”

Construction of Halofunctionalized Indenes via a Cascade Prins‐Nazarov Cyclization Promoted by Dual Roles of BX3

“…BF 3 . OEt 2 ‐promoted ring opening reactions of epoxides or aziridines to produce fluorinated compounds have been reported however, BF 3 . OEt 2 ‐promoted Prins reactions of arylalkynes with carboxaldehydes for the synthesis of fluoroindenes have not yet been developed.…”

Pinacolatoboron fluoride (pinBF) is an efficient fluoride transfer agent for diastereoselective synthesis of benzylic fluorides

“…7 Despite methodological advances in stereoselective fluorination, 8 including the advent of asymmetric protocols, 9 the synthesis of stereodefined benzylic fluorides by nucleophilic fluorination is frequently hampered by competing racemization (or epimerization) due to the intermediacy of benzylic carbocations. 10,11 As part of a research programme into the utility of boron fluorides 12 and fluoroborates [13][14][15] as inexpensive, atom-economic and easily-handled nucleophilic fluorinating agents, 16 we have reported the ringopening fluorination of trans-b-substituted aryl epoxides upon treatment with BF 3 ÁOEt 2 . 12 This reaction proceeds via stereoselective S N 1-type ring opening with retention of configuration to provide benzylic fluoride building blocks, which we utilized for the synthesis of a range of b-fluoroamphetamines.…”