Recent advances in electrochemical functionalization using diazonium salts

Arenediazonium salts have gained attention in the scientific community due to their numerous synthetic applications. In the traditional method of dediazoniation of arenediazonium salts, the requirements for toxic oxidants and costly catalysts affect their cost-effectiveness and sustainability. However, recent advances in synthetic organic electrochemistry allow for the in situ reduction of arenediazonium salts, affording different functionalizations under mild reaction conditions and with a shorter reaction time. Herein, we report advances up to now of facile organic electrochemical syntheses using arenediazonium salt precursors that avoid the use of hazardous reductants.

Total Synthesis of Aqabamycin G, a Nitrophenyl Indolylmaleimide Marine Alkaloid from Vibrio sp. WMBA

The first total synthesis of the marine alkaloid aqabamycin G is disclosed. The synthetic sequence involved the stepwise addition to maleimide of an indole motif and a substituted diazo-benzenoid unit derived from acetaminophen. An alternative strategy using a protected phenol is also reported.

Diverse 3-Methylthio-4-Substituted Maleimides through a Novel Rearrangement Reaction: Synthesis and Selective Cell Imaging

A transition metal-free protocol for the preparation of fluorescent and non-fluoresent 3-methylthio-4-arylmaleimides in a single step through a new rearrangement from thiazolidine-2,4-diones is described. By employing the optimized reaction conditions, a broad scope of derivatives was prepared in ≤97% yield. The reaction tolerated several substituted aryl groups, including the challenging preparation of pyridyl-containing derivatives. A series of control experiments strongly suggested that the new rearrangement involves a key isocyanate intermediate and a further reaction with in situ-generated methylthiomethyl acetate. The photophysical properties of some of the synthesized derivatives as well as their use in live cell imaging were also investigated, revealing that some of the substituted maleimides are capable of selectively staining different regions of the cells.

HFIP-promoted Michael reactions: direct para-selective C-H activation of anilines with maleimides

The Michael reaction is widely used for the C-C coupling of electron-poor olefins and C(sp3)-H pronucleophiles. Herein, an effective Michael reaction approach between electron-rich aromatic and heteroaromatic substrates as C(sp2)-H nucleophiles with maleimides as electrophiles in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was first presented without the need for any additional metal catalysts or reagents. This reaction provides a concise and environmentally friendly strategy for the facile construction of 3-aryl succinimides from N,N-disubstituted anilines and maleimides with high para selectivity.

A deciduous directing group approach for the addition of aryl and vinyl nucleophiles to maleimides

A Rh(iii)-catalyzed C–H activation followed by conjugate addition to maleimides, using carboxylic acid as a traceless/deciduous directing group, to formally furnish a C_sp2–C_sp3 bond is presented.

Phospha-Michael addition reaction of maleimides employing N-heterocyclic phosphine-thiourea as a phosphonylation reagent: synthesis of 1-aryl-2,5-dioxopyrrolidine-3-yl-phosphonate derivatives

The phospha-Michael addition reaction of maleimides with NHP-thiourea under catalyst and additive free conditions has been developed for desymmetrization of maleimides.