Cross-Coupling Hydrogen Evolution Reaction in Homogeneous Solution without Noble Metals

Abstract

A highly efficient noble-metal-free homogeneous system for a cross-coupling hydrogen evolution (CCHE) reaction is developed. With cheap, earth-abundant eosin Y and molecular catalyst Co(dmgH)2Cl2, good to excellent yields for coupling reactions with a variety of isoquinolines and indole substrates and H2 have been achieved without any sacrificial oxidants. Mechanistic insights provide rich information on the effective, clean, and economic CCHE reaction.

TMSCl-Catalyzed Tandem Reaction of Dihydroisobenzofuran Acetals with Indoles

“…Indoles with methyl, methoxy, benzyloxy, fluoro, chloro, and bromo substituents at C5 and C6 positions also provide satisfactory yields (71−86%) ( Table 2, entries 3-11). C7-methyl, methoxy, and fluoro substituted indoles afford the products in 69-88% yields ( Table 2, entries [12][13][14]. The next was focused on different dihydroisobenzofuran acetals.…”

“…Such compounds are typically prepared by metal catalyzed cross-dehydrogenative coupling. [11][12][13]. Recently, we developed an acid catalyzed dearomative arylation strategy for the synthesis of α-indolisoquinolines [14].…”

9,10-Phenanthrenedione as Visible-Light Photoredox Catalyst: A Green Methodology for the Functionalization of 3,4-Dihydro-1,4-Benzoxazin-2-ones through a Friedel-Crafts Reaction

“…[39][40][41][42] Normally, this sp 3 -C-H functionalization involves the oxidation of the amine to iminium ion, that can be attacked by various kind of nucleophiles. Nonetheless, the major number of examples are regarded to the functionalization of N-aryl tetrahydroisoquinolines, [43][44][45][46][47][48][49][50][51][52][53] N,N-dimethylanilines [54][55][56][57][58] and N-aryl glycine derivatives. [59][60][61][62][63] Hence, exploring other substrates is highly desirable.…”

Oxidative Coupling – Bonding between Two Nucleophiles

“…Oxygen gas is perhaps the most appealing oxidant for oxidative cross-couplings, as H 2 O is usually the side product. Recently, cross-coupling with hydrogen revolution has been demonstrated to achieve C-C and C-heteroatom bond formations in the absence of an external oxidant [18][19][20][21][22][23][24]. Those developments put forward the area of oxidative cross-coupling into more practical and more environmentally benign processes.…”