C‐Alkylation of Ketones and Related Compounds by Alcohols: Transition‐Metal‐Catalyzed Dehydrogenation

Abstract

Transition-metal-catalyzed C-alkylation of ketones and secondary alcohols, with alcohols, avoids use of organometallic or environmentally unfriendly alkylating agents by means of borrowing hydrogen (BH) or hydrogen autotransfer (HA) activation of the alcohol substrates. Water is formed as the only by-product, thus making the BH process atom-economical and environmentally benign. Diverse homogeneous and heterogeneous transition-metal catalysts, ketones, and alcohols can be used for this transformation, thus rendering the BH process promising for replacing those procedures that use traditional alkylating agents. This Minireview summarizes the advances during the last five years in transition-metal-catalyzed BH α-alkylation of ketones, and β-alkylation of secondary alcohols with alcohols. A discussion on the application of the BH strategy for C-C bond formation is included.

Catalytic reduction of 1,4‐benzoquinone to hydroquinone via [FeFe]‐hydrogenase model complexes under mild conditions

“…Based on the present experimental results and previous studies, we speculated that the catalytic reaction can be divided into two parts: hydrogenation reaction and methoxylation of BQ. If the two parts are interrelated, as shown in Scheme , under the action of the catalyst, BQ and CH 3 OH react to generate HQ.…”

Iron‐Catalyzed Borrowing Hydrogen C‐Alkylation of Oxindoles with Alcohols

“…[1] Furthermore, oxindoles that are mono-o rd isubstituted at the C3p osition are commonly employed in drug discovery programs, [2] with examples including the development of HIV-1n on-nucleoside reverset ranscriptase inhibitors, spirocyclic compounds with anti-cancer and anti-inflammatory properties, and antagonists of progesterone and 5hydroxytryptamine 7 (5-HT 7 )r eceptors (Scheme 1A). [4] Recent progress in this area has provided alternatives to commonly employed precious-metal catalysts through the development of catalysts based on earth-abundant first-row transition metals. [3] An alternative approache mployst he borrowing hydrogen (BH) principle, also known as hydrogen autotransfer,w hich allows bench-stable and inexpensive alcohols to be used as alkylating agents, generating water as the sole byproduct.…”

Bidentate Ru(II)‐NC Complexes as Catalysts for α‐Alkylation of Unactivated Amides and Esters

“…[1] For this transformation, the deprotonated carboxylic acid derivatives generated by the addition of strong bases, are always used as nucleophilic reagents traditionally, to react with toxic alkyl halides, thus leading to the formation of stoichiometric amount of inorganic salt as waste. [3] This strategy uses primary alcohols as alkylating agents and water is released as the only by-product. [3] This strategy uses primary alcohols as alkylating agents and water is released as the only by-product.…”