Borrowing-Hydrogen Processes

Saidi O, Blacker AJ, Lamb GW et al (2010) Borrowing hydrogen in water and ionic liquids iridium-catalyzed alkylation of amines with alcohols. Org Process Res Dev 14(4) 1046-1049... 

Jumde VR, Gonsalvi L, Taddei M et al (2015) A ruthenium-based catalytic system for a mild borrowing-hydrogen process Eur J Org Chem 2015(8) 1829-1833... 

Figure 13.11 NHC-based catalysts for borrowing-hydrogen processes.

Starting directly from unprotected amines and alcohols, N- and C(3)-dialkylation took place. This overall transformation resulted from dehydrogenation of the alcohol via hydrogen transfer followed by a mechanism similar to the previous one involving borrowing hydrogen processes (Scheme 41) [36]. 

A-Alkylation of amides and amines and dehydrative -alkylation of secondary alcohols and a-alkylation of methyl ketones " have been carried out by an activation of alcohols by aerobic oxidation to aldehydes, with copper(II) acetate as the only catalyst. A relay race process rather than the conventional borrowing hydrogen-type mechanisms has been proposed for the aerobic C-alkylation reactions, based on results of mechanistic studies. A Winterfeldt oxidation of substituted 1,2,3,4-tetrahydro-y-carboline derivatives provides a convenient and efiflcient method for the synthesis of the corresponding dihydropyrrolo[3,2-fc]quinolone derivatives in moderate to excellent yields. The generality and substrate scope of this aerobic oxidation have been explored and a possible reaction mechanism has been proposed. Direct oxidative synthesis of amides from acetylenes and secondary amines by using oxygen as an oxidant has been developed in which l,8-diazabicyclo[5.4.0]undec-7-ene was used as the key additive and copper(I) bromide as the catalyst. It has been postulated that initially formed copper(I) acetylide plays an important role in the oxidative process. Furthermore, it has been postulated that an ct-aminovinylcopper(I) complex, the anti-Markovnikov hydroamination product of copper acetylide, is involved in the reported reaction system. Copper(I) bromide... 

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