Research Overview 

Tremendous efforts will continue towards developing novel synthetic methodologies with improved efficiencies and are more environmentally benign. Simultaneously, the focus has preserved such steady and impressive goals and is also equally well aware of the rapidly changing nature of chemical synthesis and related domains. 

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Green chemistry is a new way of looking at photoredox catalysis and electrochemical synthesis, offering significant environmental and economic advantages over conventional synthetic methods. From the perspective of the rising need for green and sustainable synthetic methodologies, photocatalytic and electrochemical transformations presently the hottest research area in advanced chemical synthesis.

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Current Overview of our Research

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1. Thiosulfonates (RS–SO2R1) are the privileged class of organosulfur substrates andhave been  successfully demonstrated as a versatile precursor in organic synthesis.

 

1. Sulfenylating agent: A novel oxidative difunctionalization of b-iodovinyl sulfones with thiosulfonates and NaOAc in DMF has been developed to access a wide range of b-keto thiosulfones (Eur. J. Org. Chem. 2019, 3771). We have successfully developed an efficient and environmentally benign sequential one-pot protocol for the synthesis of 3-sulfenylimidazo[1, 2-a]pyridines using series of α-bromomethyl ketones, 2-aminopyridines and thiosulfonates (Asian J. Org. Chem., 2019, 8, 2269). Cu(I)-catalyzed interrupted click-sulfenylation of O-/N-propargyl benzyl thiosulfonates with organic azides has been disclosed to provides a range of triazole-fused eight-membered heterocycles in good to high yields (Adv. Synth. Catal. 2022, 364, 319).

2. Sulfonylation agent: A highly regioselective, iodine-mediated sulfonylation of NH-1,2,3-triazoles using sodium thiosulfonates has been demonstrated to provide N-sulfonyl triazoles in moderate to high yields (Tetrahedron Lett. 2018, 59, 2014). Cs2CO3-promoted radical sulfonylation of Morita–Baylis–Hillman (MBH) bromides with thiosulfonates under mild conditions to access a series of allyl sulfones (SynOpen, 2021, 5, 91).

3. Thiosulfonylation agent: (i) A new and highly efficient vicinal thiosulfonylation of 1,1-dibromo-1-alkenes or 1-bromoalkynes with thiosulfonates in the presence of cesium carbonate has been developed for the synthesis of a wide range of (E)-1,2-thiosulfonylethenes in moderate to high yields (Adv. Synth. Catal. 2019, 361, 1587; Synthesis, 2021, 53, 2850). (ii) A unique phenylboronic acid-catalyzed dimerization–sulfonylation of S-benzyl thiosulfonates has been disclosed for tandem construction of S–S and C–S bonds to access a wide range of benzyl disulfanylsulfone derivatives in high to excellent yields (Org. Biomol. Chem. 2020, 18, 3243). (iii) A unique Au-catalyzed atom transfer radical cyclization (ATRC) of ortho-alkynyl benzyl thiosulfonates has been successfully achieved, producing sulfonyl-derived isothiochromenes as a major product through a favored 6-endo-dig cyclization (J. Org. Chem. 2025, 90, 3628−3638).

4. Moreover, the allyl thiosulfonates were readily-assembled using the Morita-Baylis-Hillman allyl bromides and sodium arylthiosulfonates without any reagent/catalyst (RSC Adv. 2018, 8, 40446). The allyl thiosulfonates were successfully transformed into a set of two synthetically viable allyl disulfanes in the presence of Cs2CO3 is reported.​​​​​​

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(2) Unprecedented reactivity of ‘beta-iodovinyl sulfones’ was explored for the first time in our laboratory

1. The palladium-catalyzed annulation between β-iodovinyl sulfones and 2-halophenols involves oxa-Michael addition-elimination and intramolecular Heck reaction, leading to form 2,3-disubstituted benzofurans in good to high yields (Adv. Synth. Catal. 2020, 362, 1317).

2. A unique vicinal bisthiolation of (E)-b-iodovinyl sulfones with thiols under the influence of K2CO3/DMSO at room temperature for quick assembly of (E)-1,2-dithio-1-alkenes is demonstrated (J. Org. Chem. 2022, 87, 3934).

3. A novel cycloannulation between β-iodovinyl sulfones and N-tosyl-aminopyridines was also successfully developed for the synthesis of 3-sulfonylpyrazolo[1,5-a]pyridines (Org. Biomol. Chem. 2022, 20, 4331).

4. K3PO4-mediated cycloannulation of (E)-β-iodovinyl sulfones with ortho-hydroxy chalcones/ortho-hydroxy cinnamates has been realized to access 2,3,4-trisubstituted-4H-benzopyran derivatives (Adv. Synth. Catal. 2022, 364, 4080).

5. Base-mediated oxa-Michael addition-elimination of (E)-β-iodovinyl sulfones with ortho-alkynylphenols, followed by cycloisomerization and unique stereoselective sulfonyl migration in one-pot, is realized under the influence of Mn(OAc)3·2H2O and a broad range of vinyl sulfone-tethered chromenes in high yields (Org. Lett. 2023, 25, 2207).

6. A general and highly efficient Pd(OAc)2-catalyzed intramolecular cyclization and vinylation of ortho-alkynylphenols/ortho-alkynylanilines with (E)-β-iodovinyl sulfones under mild reaction conditions for the diversity-oriented synthesis of vinyl sulfone-tethered benzofurans and indoles in good to high yields (J. Org. Chem. 2023, 88, 8889).

7. We present an efficient and transition-metal-free [4+1]-thioannulation of sulfonyl-tethered 1,3-enynes with Na2S in the presence of Cs2CO3 to generate 2,4-disubstituted thiophenes in good to high yields. We also established a formal [3+2]-cycloaddition of 1,3-sulfonylenynes with NaN3 under metal- and base-free conditions to synthesize vinyl sulfone-containing 1,2,3-NH-triazole derivatives in moderate to high yields (Asian J. Org. Chem., 2024, 13, e202400211).

8. We have successfully demonstrated a highly efficient base-mediated cascade annulative-sulfonylation of 4-(pseudo)halo-2-aminopyridines with (E)-β-iodovinyl sulfones in polyethylene glycol. This innovative method features an unexpected sulfonyl shift, enabling the first preparative synthesis of 7-sulfonyl-derived imidazo[1,2-a]pyridines in good to high yields. Distinctively, other substituted 2- aminopyridines undergo annulative-desulfonylation with (E)-β-iodovinyl sulfones, leading to the formation of 3-substituted imidazo[1,2-a]pyridines in moderate to high yields (J. Org. Chem. 2025, 90, 15942−15955).

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