Tf2O/DMSO-mediated dual activation of aryl phosphinate to access various aryl phosphonates

A metal-free method for the dual activation of aryl phosphinate has been developed; the P-H and P-O bonds are sequentially activated by the Tf2O/DMSO system. Without the requirement of metals and unstable P-reagents, this one-pot procedure provides a convenient and practical access to a variety of aryl phosphonates. A mechanism involving twice generation of electrophilic P-species and two SN-processes is proposed on the basis of the control experiments.

Silver-catalyzed decarboxylative cyclization for the synthesis of substituted pyrazoles from 1,2-diaza-1,3-dienes and α-keto acids

A silver-catalyzed decarboxylative cyclization process has been developed for the synthesis of substituted pyrazoles from the readily available 1,2-diaza-1,3-dienes and α-keto acids. Under the optimized conditions, a series of multisubstituted pyrazoles were well prepared in moderate to good yields. In addition, the synthetic utility of this protocol has been demonstrated by synthesizing analogs of FDA approved drugs such as anti-inflammatory drug, lonazolac and antiobesity drug, rimonabant.

Nickel-Catalyzed, para-Selective, Radical-Based Alkylation of Aromatic Ketones

A direct, para-selective, radical-based alkylation of aromatic ketones with alkanes has been developed using a nickel catalyst with oxamide as the ligand. Acetophenones bearing electron-withdrawing substituents were functionalized directly with simple alkanes with high para-selectivity while acetophenones with electron-donating groups were mainly para-functionalized. A mechanistic study indicated that C-H bond activation of the aromatic ring may be the rate-determining step of the reaction.

Direct C-H Phosphonylation of Electron-Rich Arenes and Heteroarenes by Visible-Light Photoredox Catalysis

The direct transformation of ubiquitous, but chemically inert C-H bonds into diverse functional groups is an important strategy in organic synthesis that improves the atom economy and faclitates the preparation and modification of complex molecules. In contrast to the wide applications of aryl phosphonates, their synthesis via direct C-H bond phosphonylation is a less explored area. We report here a general, mild, and broadly applicable visible-light photoredox C-H bond phosphonylation method for electron-rich arenes and heteroarenes. The photoredox catalytic protocol utilizes electron-rich arenes and biologically important heteroarenes as substrates, [Ru(bpz)₃ ][PF₆ ]₂ as photocatalyst, ammonium persulfate as oxidant, and trialkyl phosphites as the phosphorus source to provide a wide range of aryl phosphonates at ambient temperature under very mild reaction conditions.

Straightforward synthesis of functionalized chroman-4-ones through cascade radical cyclization-coupling of 2-(allyloxy)arylaldehydes

A novel and direct approach to synthesize a series of phosphonate, azide and hydroxy functionalized chroman-4-ones has been developed. The transformation appears to proceed via an intramolecular addition of in situ generated acyl radical onto alkene, followed by a radical/radical cross coupling.

Silver(i)-promoted C5–H phosphonation of 8-aminoquinoline amides with H-phosphonates

An efficient protocol for silver(i)-promoted C5–H phosphonation of 8-aminoquinoline amides with dialkyl H-phosphonates was developed.

Cobalt catalysed, copper assisted C(sp2)–P cross coupling

An efficient C(sp²)–P cross coupling has been achieved using a Co/Cu catalytic system for access to vinyl and aryl phosphonates.

Dehydrogenative coupling involving P(O)–H bonds: a powerful way for the preparation of phosphoryl compounds

This Frontier highlights the recent progress in the preparation of organophosphorus compounds via transition metal-catalysed dehydrogenative couplings of P(O)H compounds with Z–H compounds.