Henry Reaction Revisited. Crucial Role of Water in an Asymmetric Henry Reaction Catalyzed by Chiral NNO-Type Copper(II) Complexes

Henry Reaction Revisited. Crucial Role of Water in an Asymmetric Henry Reaction Catalyzed by Chiral NNO-Type Copper(II) Complexes Full article

Journal

Inorganic Chemistry
ISSN: 0020-1669 , E-ISSN: 1520-510X

Output data

Year: 2019, Volume: 58, Number: 16, Pages: 11051-11065 Pages count : 15 DOI: 10.1021/acs.inorgchem.9b01574

Authors

Larionov Vladimir A. ^1,2 , Yashkina Lidiya V. ¹ , Medvedev Michael G. ^1,3,4 , Smol’yakov Alexander F. ^1,5 , Peregudov Alexander S. ¹ , Pavlov Alexander A. ¹ , Eremin Dmitry B. ^3,6 , Savel’yeva Tat’yana F. ¹ , Maleev Victor I. ¹ , Belokon Yuri N. ¹

Affiliations

1	A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Street 28, 119991 Moscow, Russian Federation
2	Department of Inorganic Chemistry, Peoples’ Friendship University of Russia (RUDN University), Miklukho-Maklaya Street 6, 117198 Moscow, Russian Federation
3	N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky prospect 47, 119991 Moscow, Russian Federation
4	National Research University Higher School of Economics, Myasnitskaya Street 20, 101000 Moscow, Russian Federation
5	Plekhanov Russian University of Economics, Stremyanny per. 36, 117997 Moscow, Russian Federation
6	The Bridge@USC, University of Southern California, 1002 Childs Way, Los Angeles, California 90089-3502, United States

Chiral copper(II) and cobalt(III) complexes (1–5 and 6, respectively) derived from Schiff bases of (S)-2-(aminomethyl)pyrrolidine and salicylaldehyde derivatives were employed in a mechanistic study of the Henry reaction-type condensation of nitromethane and o-nitrobenzaldehyde in CH2Cl2 (CD2Cl2), containing different amounts of water. The reaction kinetics was monitored by 1H and 13C NMR. The addition of water had a different influence on the activity of the two types of complexes, ranging from a crucial positive effect in the case of the copper(II) complex 2 to insignificant in the case of the stereochemically inert cobalt(III) complex 6. No experimental support was found by 1H NMR studies for the classical Lewis acid complexation of the carbonyl group of the aldehyde by the central copper(II) ion, and, moreover, density functional theory (DFT) calculations support the absence of such coordination. On the other hand, a very significant complexation was found for water, and it was supported by DFT calculations. In fact, we suggest that it is the Brønsted acidity of the water molecule coordinated to the metal ion that triggers the aldehyde activation. The rate-limiting step of the reaction was the removal of an α-proton from the nitromethane molecule, as supported by the observed kinetic isotope effect equaling 6.3 in the case of the copper complex 2. It was found by high-resolution mass spectrometry with electrospray ionization that the copper(II) complex 2 existed in CH2Cl2 in a dimeric form. The reaction had a second-order dependence on the catalyst concentration, which implicated two dimeric forms of the copper(II) complex 2 in the rate-limiting step. Furthermore, DFT calculations help to generate a plausible structure of the stereodetermining transition step of the condensation.

Larionov V.A. , Yashkina L.V. , Medvedev M.G. , Smol’yakov A.F. , Peregudov A.S. , Pavlov A.A. , Eremin D.B. , Savel’yeva T.F. , Maleev V.I. , Belokon Y.N.
Henry Reaction Revisited. Crucial Role of Water in an Asymmetric Henry Reaction Catalyzed by Chiral NNO-Type Copper(II) Complexes
Inorganic Chemistry. 2019. V.58. N16. P.11051-11065. DOI: 10.1021/acs.inorgchem.9b01574 WOS Scopus OpenAlex

≡ Web of science:	WOS:000482173300070
≡ Scopus:	2-s2.0-85070821336
≡ OpenAlex:	W2964596055