Ruthenium(II)-Catalyzed Site-Selective Hydroxymethylation of Indolines with Paraformaldehyde

SnCl2-catalyzed multicomponent coupling: synthesis of 1,3-oxazolidine derivatives using paraformaldehyde as a C1 feedstock

SnCl2 catalyzed the three-component coupling of aniline, epoxide, and paraformaldehyde, resulting in the synthesis of 1,3-oxazolidine derivatives. The reaction is simple and does not require any additives, bases, or oxidants, and proceeds at moderate temperature with good functional group tolerance. The scope of the utilization of paraformaldehyde as the methylene source was further extended to the synthesis of benzothiazole and 4,4'-methylenebis(N,N-dimethylaniline) using the same catalyst. A catalytic pathway was proposed based on the control experiments.

Nickel-Catalyzed Tandem Cyclization of 1,6-Diynes with Indolines/Indoles through Dual C-H Bond Activation

A nickel-catalyzed site-selective tandem cyclization of 1,6-diynes with substituted indolines or indoles through consecutive dual C-H bond activation is described. In the reaction, substituted fused indole and carbazole derivatives were observed in good to excellent yields, in which three consecutive C-C bonds formed in one pot. Later, in the presence of DDQ, the aromatization of the indoline derivative was converted to the indole derivative. A possible reaction mechanism involving dual C-H bond activation as a key step was proposed to account for the present reaction.

Construction of 1,2-dihydro-1,3,5-triazines via reactions involving amidines

1,2-Dihydro-1,3,5-triazine compounds were synthesized through three sets of reactions of amidines with, respectively, paraformaldehyde, aldehydes and N-arylnitrones under different conditions. The catalysts used in these three reactions were Cu(OAc)₂, ZnI₂ and CuCl₂·2H₂O, respectively. Most of the substrates tested for these reactions provided the target products in moderate to good yields. In the reactions involving paraformaldehyde, Cu(OAc)₂ also accelerated the release of formaldehyde from paraformaldehyde during the catalytic reaction process. In the case of the reactions involving nitrones, CuCl₂·2H₂O not only catalyzed the normal progress of the main reaction, but also promoted the reaction of nitrones to produce nitroso compounds and aldehydes.

Ruthenium(II)-Catalyzed Grignard-Type Nucleophilic Addition of C(sp2)-H Bonds to Unactivated Aldehydes

The Grignard-type nucleophilic addition of C(sp²)-H bonds to aldehydes catalyzed by high-oxidation-state transition metal complexes is limited to activated aldehydes. Herein, we report the first example of Grignard-type nucleophilic addition of C(sp²)-H bonds to unactivated aldehydes catalyzed by high-oxidation-state ruthenium(II). The reaction has mild reaction conditions and good functional group tolerance. The corresponding alcohol products are obtained in good to excellent yields.

Dimeric Manganese-Catalyzed Direct Nucleophilic Addition of C(sp2)-H Bonds to Inert Aldehydes

An efficient direct nucleophilic addition reaction of C(sp²)-H bonds to aldehydes catalyzed by a dimeric manganese has been developed. This reaction has a broad range of substrates, and high yields were also obtained with inert aliphatic aldehydes as substrates. A dimeric Mn₂(CO)₈Br₂ was proven to be a more efficient catalyst precursor than the monomeric Mn(CO)₅Br.

Synthesis of C7-Functionalized Indoles through an Aromaticity Destruction-Reconstruction Process

A process for the synthesis of C7-functionalized indoles using para-substituted 2-alkynylanilines as starting materials was reported. The process involves a dearomatization, an 1,2-addition by organic lithium or Grignard reagents, an aromatization-driven allylic rearrangement, and a cyclization. A variety of groups including alkyl, aryl, alkenyl, or alkynyl groups were selectively installed at the C7 site of indoles leading to the formation of 2,5,7-trisubstituted indoles.

KIO4 -mediated Selective Hydroxymethylation/Methylenation of Imidazo-Heteroarenes: A Greener Approach

Herein, we report a KIO₄ -mediated, sustainable and chemoselective approach for the one-pot C(sp² )-H bond hydroxymethylation or methylenation of imidazo-heteroarenes with formaldehyde, generated in situ via the oxidative cleavage of ethylene glycol or glycerol (renewable reagents) through the Malaprade reaction. In the presence of ethylene glycol, a series of 3-hydroxymethyl-imidazo-heteroarenes was obtained in good to excellent yields. These compounds are important intermediates to access pharmaceutical drugs, e.g., Zolpidem. Furthermore, by using glycerol, bis(imidazo[1,2-a]pyridin-3-yl)methane derivatives were selectively obtained in good to excellent yields.

Ru(ii)-Catalyzed C-H addition and oxidative cyclization of 2-aryl quinazolinones with activated aldehydes

The ruthenium(ii)-catalyzed cross-coupling reaction between 2-aryl quinazolinones and activated aldehydes is described. This method enables the site-selective hydroxyalkylation under redox-neutral conditions. Moreover, this protocol provides a facile access to various tetracyclic isoindoloquinazolinones by using Cu(OAc)₂ as an external oxidant via C-H addition and subsequent intramolecular cyclization. A wide substrate scope and a high level of chemoselectivity as well as broad functional group tolerance are observed.

Ru(II)-Catalyzed C-H Hydroxyalkylation and Mitsunobu Cyclization of N-Aryl Phthalazinones

Ruthenium(II)-catalyzed C(sp²)-H functionalization of N-aryl phthalazinones with a range of aldehydes and activated ketone is described. Initial formation of hydroxyalkylated phthalazinones and subsequent Mitsunobu cyclization provided facile access to biologically relevant indazolophthalazinones. The utility of this method is highlighted by synthetic transformations into a series of potentially bioactive scaffolds.

Cobalt-catalyzed hydroxymethylarylation of terpenes with formaldehyde and arenes

A cobalt(iii)-catalyzed C–H activation strategy has been developed to facilitate hydroxymethylarylation of terpenes with formaldehyde and arenes with high chemo- and regio-selectivities.

Terpenes, consisting of isoprene monomer units, represent a family of naturally abundant compounds. The difunctionalization of terpenes is highly appealing yet remains challenging, since the multiple unbiased C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds of terpenes lead to difficulty in controlling the regioselectivity. Herein, a cobalt(iii)-catalyzed C–H activation strategy has been developed to facilitate hydroxymethylarylation of terpenes with formaldehyde and arenes with high chemo- and regio-selectivities. These (chemo- and regio-) selectivities are governed by the coordination abilities of isoprene, directing groups and the steric effect. This terpene difunctionalization also features high atom and step economy through a C–H addition pathway.

Nickel-catalyzed regioselective C–H acylation of chelating arenes: a new catalytic system for C–C bond formation via a radical process and its mechanistic explorations

An unprecedented acylation at the ortho C–H bond of chelating arenes via the Ni(ii)-catalyzed cross dehydrogenative coupling strategy has been developed here.