Borrowing Hydrogen Methodology

A number of A-alkyl substituted NHC-Ru-hydride complexes were studied in this context. Ruthenecycle 73 was readily hydrogenated to 74 displaying the 

Finally, a new method was developed for the amidation of amines with primary alcohols in the presence of in situ formed [(NHC)Ru(PR3)] complexes. According to the authors, the reaction proceeded via an aldehyde formed by the dehydrogenation of the substrate, which would stay coordinated to the ruthenium centre. Subsequent attack of the amine would give a coordinated hemiaminal and p-hydride elimination from this intermediate would result in the A-alkyl amide. 

The Si-H bond is polar, and reactive, and its addition across multiple bonds, such as C=C, C=C and C=0 is an essential reaction in organo silicon chemistry. Generally trichloro- or dichlorosilanes are employed for this reaction since the reactivity of trialkylsilanes is significantly lower. 

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In 2015, Zhao and co-workers described the first dynamic kinetic asymmetric amination of alcohols via borrowing hydrogen methodology under the cooperative catalysis of iridium complex 25 and chiral phosphoric acid 27 (Schemes 31, 32) [179]. The authors proposed that, initially, the two stereocenters in the alcohols were both racemized to ketone by the first oxidation, followed by tautomerization of the iminium intermediates 28 and 30 through enamine intermediate 29. Then, the... 

Shimizu K1 (2015) Heterogeneous catalysis for the direct synthesis of chemicals by borrowing hydrogen methodology. Catal Sci Technol 5(3) 1412-1427... 

Nixon TD, Whittlesey MK, Williams JMJ (2(X)9) Transition metal catalysed reactions of alcohols using borrowing hydrogen methodology. Dalton Trans 5 753-762... 

Hamid MHSA, Allen CL, Williams JMJ et al (2009) Ruthenium-catalyzed V-alkylation of amines and sulfonamides using borrowing hydrogen methodology. J Am Chem Soc 131(5) 1766-1774... 

Watson AJ, Maxwell AC, Williams JM (2011) Borrowing hydrogen methodology for amine synthesis under solvent-free microwave conditions. J Org Chem 76(7) 2328-2331... 

Enyong AB, Moasser B (2014) Ruthenium-catalyzed Al-alkylation of amines with alcohols under mild conditions using the borrowing hydrogen methodology. J Org Chem 79(16) 7553-7563... 

Liu H, Chuah G-K, Jaenicke S (2012) A-alkylation of amines with alcohols over alumina-entrapped Ag catalysts using the borrowing hydrogen methodology. J Catal 292 130-137... 

Dixit M, Mishra M, Joshi PA et al (2013) Clean borrowing hydrogen methodology using hydro-talcite supported copper catalyst. Catal Commun 33 80-83... 

Zhang Y, Lim CS, Zhao Y et al (2014) Catalytic enantioselective amination of alcohols by the use of borrowing hydrogen methodology cooperative catalysis by iridium and a chiral phosphoric acid. Angew Chem Int Ed 53(5) 1399-1403... 

Saidi O, Marsden SP, Williams JM et al (2009) Selective amine cross-coupling using iridium-catalyzed borrowing hydrogen methodology. Angew Chem Int Ed 48(40) 7375-7378... 

Along with their high activity in the borrowing hydrogen methodology (see Section 8.4.1), complexes of general composition [(NHC)Ir(Cp )]... 

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