ModifiedB‐Alkylcatecholboranes as Radical Precursors

Abstract

Generation of radicals from B-alkylcatecholboranes represents an efficient tin-free procedure for the generation of alkyl radicals. A modified version of this method has been developed. The simple catechol is replaced by a dihydroxylated tetrahydroisoquinoline, which can be separated from the reaction products by simple extraction with an aqueous acid solution. The modified alkyl radical precursors are easily prepared from alkenes by hydroboration with BH 3 ·Me 2 S fol-

Strongly Luminous Tetranuclear Gold(I) Complexes Supported by Tetraphosphine Ligands, meso‐ or rac‐Bis[(diphenylphosphinomethyl)phenylphosphino]methane

“…Many olefins were compatible with this methodology with use of di‐ tert ‐butylhyponitrile (DTBHN) as radical initiator at 40 °C. Similarly good yields were obtained with use of borane dimethylsulfide complexes and molecular oxygen as radical initiator in place of catecholborane 36. These conditions were also successful for the alkynylation of silyl radicals (from silylboranes) 37…”

Practical C−H Functionalization of Quinones with Boronic Acids

“…20 Most recently, Renaud has accomplished the coupling of customized catecholboranes to quinones followed by reoxidation. 21 Notably, arylboronic acids have recently been coupled to electron-deficient olefins in excess via a presumed radical mechanism with stoichiometric manganese(III) acetate (no quinone examples given). 22 Inspired by our recent discovery of the silver-catalyzed addition of arylboronic acids to protonated heterocycles, 23 and given the inherent reactivity of quinones with radicals, 1,2 it was reasoned that the same reactive intermediate generated from the boronic acid precursors could interact with other electrophiles such as quinones.…”

N-heterocyclic carbene-catalyzed rearrangements of vinyl sulfones

“…12 Our survey of standard Lewis bases for this process, such as 1,4-diazabicyclo[2.2.2]octane (DABCO) and triphenylphosphine, revealed there was poor and incomplete conversion when compared to the NHC catalyst generated from azolium catalyst A and sodium tert -butoxide. 13 Trans -1,2-bis(arylsulfonyl)ethylene has been used in organic synthesis, 14 but its preparation typically involves the use of vinyl chloride gas. 15 Alternatively, the straightforward preparation of 1,1-bis(phenylsulfonyl)ethylene involves paraformaldehyde, piperidine, and acid.…”