Synthesis of 6-(Arylthio)phenanthridines by Copper-Catalyzed Tandem Reactions of 2-Biaryl Isothiocyanates with Diaryliodonium Salts

Isothiocyanates: happy-go-lucky reagents in organic synthesis

Owing to their unique structural features, isothiocyanates (ITCs) are a class of highly useful and inimitable reagents as the -NCS group serves both as electrophile and nucleophile in organic synthesis. ITCs share a rich legacy in organic, medicinal, and combinatorial chemistry. Compared to their oxygen equivalents, isocyanates, ITCs are easily available, less unpleasant, and somewhat less harmful to work with (mild conditions) which makes them happy-go-lucky reagents. Functionalized ITCs can finely tune the reactivity of the -NCS group and thus can be exploited in the late-stage functionalization processes. This review's primary aim is to outline ITC chemistry in the construction and derivatization of heterocycles through the lens of sustainability. For ease and brevity, the sections are divided based on reactive centers present in functionalized ITCs and modes of cyclisation. Scrutinizing their probable unexplored directions for future research studies is also addressed.

Visible-Light-Mediated Annulation/Thiolation of 2-Isocyanobiaryls with Disulfides to Organoylthiophenanthridines Derivatives

A visible-light-induced annulation/thiolation of 2-isocyanobiaryls with dialkyl(aryl)disulfides has been established, delivering a sustainable and atom-economic route to 6-organoylthiophenanthridines with wild functional group tolerance and good to excellent yields under oxidant-, base-, and transition-metal-free conditions.

A unified approach to benzo[c]phenanthridines via the cascade dual-annulation/formylation of 2-alkynyl/alkenylbenzonitriles

A base-mediated versatile cascade dual-annulation and formylation of 2-alkenyl/alkynylbenzonitriles with 2-methylbenzonitriles has been established for the construction of four different classes of amino and amido substituted benzo[c]phenanthridines and benzo[c]phenanthrolines. The synthesized molecules could be of utmost relevance in pharmaceuticals. The transformation uses the solvent DMF as the formyl source for synthesis of the amido-substituted scaffolds. This transition-metal-free unique strategy enables the formation of multiple C-C and C-N bonds in one pot at room temperature.

Cu-catalyzed [2 + 2 + 1] cascade annulation of vinyl iodonium salts with elemental sulfur/selenium for the modular synthesis of thiophenes and selenophenes

The Cu-catalyzed [2 + 2 + 1] regioselective synthesis of thiophenes/selenophenes was realized from aryl-vinyl iodonium salts and elemental sulfur/selenium.

Base-promoted Cyclization Reaction of o-Isothiocyanato Arylacetylenes and Aroylacetonitriles: Easy Access to Benzo[d][1,3]thiazines

A green and efficient synthesis of benzo[d][1,3]thiazines through base-promoted cyclization reaction of o-isothiocyanato arylacetylenes with aroylacetonitriles has been developed. This protocol displays high step economy and efficiency, and tolerates various...

Design, Synthesis, and in vitro Evaluation of Tubulin-Targeting Dibenzothiazines with Antiproliferative Activity as a Novel Heterocycle Building Block

We prepared a series of free NH and N-substituted dibenzonthiazines with potential anti-tumor activity from N-aryl-benzenesulfonamides. A biological test of synthesized compounds (59 samples) was performed in vitro measuring their antiproliferative activity against a panel of six human solid tumor cell lines and its tubulin inhibitory activity. We identified 6-(phenylsulfonyl)-6H-dibenzo[c,e][1,2]thiazine 5,5-dioxide and 6-tosyl-6H-dibenzo[c,e][1,2]thiazine 5,5-dioxide as the best compounds with promising values of activity (overall range of 2-5.4 μM). Herein, we report the dibenzothiazine core as a novel building block with antiproliferative activity, targeting tubulin dynamics.

Fast construction of isoquinolin-1(2H)-ones by direct intramolecular C-H/N-H functionalization under metal-free conditions

The general protocol for the synthesis of isoxazolidine-fused isoquinolin-1(2H)-ones was established with the help of bench stable hypervalent iodine reagent PIDA. Polycyclic six-, seven- and eight-membered N-heterocycles can be rapidly synthesized from available amides under metal-free conditions within 1 min at room temperature through C-H/N-H functionalization. Moreover, the protocol has the merits of broad substrate scope, atom economy and operational simplicity.

Intramolecular dehydrogenative C–S bond coupling of thioamides to form 1,3-benzothiazines under metal-free conditions

A new protocol for the synthesis of 1,3-benzothiazines was developed through direct intramolecular dehydrogenative C–S bond coupling.

A ruthenium-catalyzed free amine directed (5+1) annulation of anilines with olefins: diverse synthesis of phenanthridine derivatives

A ruthenium(ii)-catalyzed cross-ring (5+1) annulation between 2-aminobiphenyls and activated olefins is disclosed for succinct synthesis of valuable phenanthridine scaffolds.

Cu-Catalyzed π-Core Evolution of Benzoxadiazoles with Diaryliodonium Salts for Regioselective Synthesis of Phenazine Scaffolds

The Cu-catalyzed regioselective synthesis of phenazine N-oxides was realized from benzoxadiazoles and diaryliodonium salts. The process was initiated by the electrophilic arylation of benzoxadiazoles with diaryliodonium salts and followed by benzocyclization reactions. The further reduction of N-oxides in situ to phenazine scaffolds and deviation to organic fluorescent materials were readily accomplished.

Engineered C-S Bond Construction

Due to the versatile applications of thioethers and thioesters in organic synthesis, medicinal chemistry, the pharmaceutical industry, and materials science, recently the construction of C-S bonds has emerged as the forefront in the field of cross-coupling reactions. Enough progress has been made in this direction by using both metal catalysis and other alternative processes. A brief review of the recent developments in the area of C-S coupling reaction is described.

Additive-Free Pd-Catalysed C-2 Arylation of Tryptophan Derivatives with Diaryliodonium Salts

An efficient, mild and Pd-catalysed C-2 arylation of Fmoc-L-tryptophan with diaryliodonium salts has been developed, giving easy access to C-2 arylated tryptophan derivatives. This protocol tolerates a variety of functional groups and proceeds smoothly in high yields without any additives. In addition, the chemoseletive C–H arylation with unsymmetrical salts is described.

Rapid synthesis of polysubstituted phenanthridines from simple aliphatic/aromatic nitriles and iodo arenes via Pd(ii) catalyzed domino C–C/C–C/C–N bond formation

An efficient method has been developed for the synthesis of polysubstituted phenanthridiene via palladium catalyzed nucleophilic addition of aryl iodides to nitriles followed by dual C–H activation.

A copper-catalyzed arylation/nucleophilic addition/fragmentation/C–S bond formation cascade: synthesis of bis(arylthio)imines

A new arylation/nucleophilic addition/fragmentation/C–S bond formation cascade was developed using isothiocyanates and diaryliodonium salts.

Metal-Free Direct α-Selective Arylation of Boron Dipyrromethenes via Base-Mediated C-H Functionalization

A metal-free direct α-selective arylation of BODIPYs has been developed based on base-mediated C-H functionalization with easily accessible diaryliodonium salts, which provides a straightforward facile access to a variety of α-arylBODIPY dyes. The α-regioselectivity was confirmed by X-ray analysis, and was studied by DFT calculation. The resultant dyes show strong absorption and emission over a broad range of spectra tunable via the simple variation of the diaryliodonium salts.

Visible light-mediated intramolecular C–H arylation of diazonium salts of N-(2-aminoaryl)benzoimines: a facile synthesis of 6-arylphenanthridines

6-Arylphenanthridines were synthesized in good to excellent yields from inexpensive and environmentally benign N-(2-aminoaryl)-diphenylmethanimine as a starting material under visible light-photocatalyzed conditions.

Copper-catalyzed tandem arylation–cyclization of 2-alkynylaryl isothiocyanates with diaryliodonium salts: an efficient synthesis of thiochromeno[2,3-b]indoles

A Cu-catalyzed arylation–cyclization approach is developed for the synthesis of thiochromeno[2,3-b]indoles through the S-arylation, 5-endo-trig cyclization, and Friedel–Crafts-type cyclization sequence.

Synthesis of benzo[1,3]oxazines via copper(i)-catalyzed cascade annulation of nitriles, aldehydes and diaryliodonium salts

A copper(i)-catalyzed one-pot [2 + 2 + 2] cascade annulation reaction of diaryliodoniums, nitriles, and aldehydes has been developed for the efficient synthesis of 2,4-substituted benzoxazine derivatives.

Amaryllidaceae and Sceletium alkaloids

The latest progress on the isolation, identification, biological activity and synthetic studies of the structurally diverse alkaloids from plants of family Amaryllidaceae has been summarized in this review.

Arylation with Diaryliodonium Salts

This chapter focuses on recent developments in metal-free and metal-catalyzed arylations with diaryliodonium salts (diaryl-λ3-iodanes). Synthetic routes to diaryliodonium salts are briefly described, and chemoselectivity trends with unsymmetric iodonium salts are discussed.

A Mild and General One-Pot Synthesis of Densely Functionalized Diaryliodonium Salts

Diaryliodonium salts are powerful and widely used arylating agents in organic chemistry. Here we report a scalable, synthesis of densely functionalized diaryliodonium salts from aryl iodides under mild conditions. This two-step, one-pot process has remarkable functional group tolerance, is compatible with commonly employed acid-labile protective group strategies, avoids heavy metal and transition metal reagents, and provides a direct route to stable precursors to PET imaging agents.

Yb(OTf)3 catalyzed [3 + 2] annulations of D–A cyclopropanes with β-oxodithioesters: a regioselective synthesis of tetrahydrothiophenes

An efficient approach to synthesis tetrahydrothiophenes was developed through the reaction of β-oxodithioesters and D–A cyclopropanes catalyzed by Yb(OTf)₃. This methodology was highly regioselective.