H₂O Activation for Hydrogen‐Atom Transfer: Correct Structures and Revised Mechanisms

Abstract

Scheme 3. Bond dissociation energies (BDE) of 2 b·THF, 3 a·THF, and 3 b·3 THF by DFT calculations (B3LYP-d/def2-TZVPP) with COSMO [17] (e = 7.6).

Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions

“…The groundstate neutral electron donors used by Murphy 14,15 and the alkyland stannyl-cobaloxime catalysts developed by Careirra 16 have successfully generated alkyl radicals from alkyl iodides. In addition, several new hydrogen atom donors have been introduced, such as N-heterocyclic carbene boranes 17 and water in the presence of Et 3 B 18 or Ti(III) salts 19 . Ultimately, the goal is to develop a mild and efficient radical reductive deiodination protocol with broad functional group tolerance that utilizes an easy-to-handle catalyst and an inexpensive and readily accessible hydrogen atom donor.…”

Activation of O−H and C−O Bonds in Water and Methanol by a Vanadium‐Bound Thiyl Radical

“…Recently, it was also found that O−H bond can be weakened via water coordination to a Mo complex, then activated with the evolution of H 2 . H 2 O is weakened and activated by coordination to a titanium center or through the second coordination sphere interaction in [Cp 2 TiCl], thus serving as a hydrogen‐atom transfer reagent . In this work, we demonstrate that an isolated vanadium‐bound thiyl radical species has the reactivity to activate H 2 O and CH 3 OH through the cleavage of strong O−H and C−O bonds.…”

Cp2TiCl/D2O/Mn, a formidable reagent for the deuteration of organic compounds

“…This SET is capable of promoting and/or catalyzing several transformations in organic chemistry [ 17 – 25 ]. One of the most relevant transformations is the H/D-atom transfer from H 2 O/D 2 O to carbon radicals (pathway A) (obtained from epoxides [ 26 – 28 ], ozonides [ 29 ] or activated halides [ 30 ] and Cp 2 TiCl/Mn), to intermediate titanaoxiranes (pathway B) [ 31 – 32 ] (obtained from carbonyl compounds and Cp 2 TiCl/Mn), and to late transition metals (pathway C) [ 33 ] in a process mediated by Cp 2 TiCl/Mn/H 2 O or D 2 O which allows for the reduction of alkenes or alkynes ( Scheme 1 ).…”