Synthesis of benzofused S-Heterocycles and similar compounds
A simple catalytic system, in which PdCl2 is the sole metal catalyst and DMSO functions as an oxidant and solvent, enables a synthesis of dibenzothiophenes in high yields from 2-biphenylthiols. This transformation offers broad substrate scope and operational simplicity.
T. Zhang, G. Deng, H. Li, B. Liu, Q. Tan, B. Xu, Org. Lett., 2018, 20, 5439-5443.
An operationally simple and efficient AgOTf-promoted tandem olefin isomerization/intramolecular hydroamination of 1,1-disubstituted alkenyl amines provides diverse 2-alkyl-substituted 1,3-X,N-heterocycles in very good yields through chemo- and regioselective C(sp3)-N bond formation with high atom economy. The reaction offers high functional group tolerance and broad substrate scope.
Y. H. Kim, D. B. Kim, S. W. Youn, J. Org. Chem., 2022, 87, 11919-11924.
In a copper-catalyzed synthesis of benzo[d]isothiazol-3(2H)-ones and N-acyl-benzothiazetidine by intramolecular dehydrogenative cyclization, a new nitrogen-sulfur bond is formed by N-H/S-H coupling. The present reaction tolerates various functional groups and gives products in gram scale.
Z. Wang, Y. Kuninobu, M. Kanai, J. Org. Chem., 2013, 78, 7337-7342.
A carbonylative cyclization of 2-iodosulfonamides using a Pd(OAc)2/Xantphos catalyst system and phenyl formate as a CO source provides various saccharin derivatives under milder reaction conditions.
S. P. Chavan, Adithyaraj. K., B. M. Bhanage, Synlett, 2017, 28, 2000-2003.
In the presence of both DMSO and a tertiary aliphatic amine (triethylamine or N-methylpiperidine), sulfur reacts directly with a wide range of 2′-nitrochalcones to provide thioaurones in high yields even at room temperature and in the absence of a transition metal catalyst.
T. B. Nguyen, P. Retailleau, Org. Lett., 2018, 20, 186-189.
The reaction of o-haloaniline derivatives and carbon disulfide in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene at 80-140˚C provides the corresponding 1,3-benzothiazole-2(3H)-thione derivatives in good yields.
Y. Fu, X. Hu, Y. Chen, Y. Yang, H. Hou, Y. Hu, Synthesis, 2012, 44, 1477-1480.
In the presence of CuCl, a three-component reaction of o-iodoanilines and K2S with TosMIC proceeded smoothly to yield the corresponding benzothiazolethiones in very good yields. Notably, isocyanide served as a carbon source and K2S functioned as a sulfur source.
P. Dang, W. Zeng, Y. Liang, Org. Lett., 2015, 17, 34-37.
A molecular iodine-catalyzed oxidative cyclization of 2-aminopyridine/amidine and isothiocyanate via N-S bond formation enables the synthesis of N-fused and 3,4-disubstituted 5-imino-1,2,4-thiadiazole derivatives at ambient temperature. This transition-metal-free protocol provides a facile and highly efficient regiospecific synthesis of various 1,2,4-thiadiazole derivatives with good to excellent yields using inexpensive I2 as a catalyst.
N. Tumula, N. Jatangi, R. K. Palakodety, S. Balasubramanian, M. Nakka, J. Org. Chem., 2017, 82, 5310-5316.
A Brønsted acid-catalyzed oxidative C-H functionalization of alkynyl thioethers provides valuable isothiochroman-3-ones in good yields under mild reaction conditions. This metal-free reaction offers a broad substrate scope and wide functional group tolerance.
Y.-Q. Zhang, X.-Q. Zhu, Y.-B. Chen, T.-D. Tan, M.-Y. Yang, L.-W. Ye, Org. Lett., 2018, 20, 7721-7725.
A one-pot method for the Sonogashira coupling and cyclization of 2-bromobenzenesulfonamides and terminal alkynes allows access to various substituted benzosultams regioselectively in excellent yields.
S. Debnath, S. Mondal, J. Org. Chem., 2015, 80, 3940-3948.
A water-gas shift reaction (WGSR) employing sodium 2-nitrobenzenesulfinates and α-bromo ketones enables a facile domino approach to benzothiazine 1,1-dioxides. This strategy is cost-effective and environmentally beneficial. The optimized reaction conditions demonstrated remarkable chemical tolerance to a wide range of electrically and sterically varied substituents on both coupling partners.
Y. Sharma, G. P. Pawar, V. D. Chaudhari, J. Org. Chem., 2023, 88, 701-710.
Treatment of various 2-amino-arylalkyl alcohols with isothiocyanates afforded thiourea intermediates, which were reacted in situ with molecular iodine in the presence of triethylamine to give 2-amino-4H-1,3-benzoxazines. The reaction of the thiourea intermediates with T3P as mild cyclodehydrating reagent and triethylamine as the base provides 2-amino-4H-1,3-benzothiazines.
V. P. R. K. Putta, N. Vodnala, R. Gujjarappa, U. Tyagi, A. Garg, S. Gupta, P. P. Pujar, C. C. Malakar, J. Org. Chem., 2020, 85, 380-396.
A copper-catalyzed three-component tandem reaction enables a convenient and practical synthesis of 1,4-benzothiazines from terminal alkynes, 2-iodophenyl isothiocyanates, and aqueous ammonia.
J.-J. Chu, B.-L. Hu, Z.-Y. Liao, X.-G. Zhang, J. Org. Chem., 2016, 81, 8647-8652.
A base-catalyzed intramolecular defluorination/O-arylation of readily available α-fluoro-β-one-sulfones provides a series of 3-fluoro-1,4-oxathiine 4,4-dioxide derivatives in very good yields. This process is triggered by a catalytic amount of tetramethylguanidine (TMG) as base and molecular sieves as both an adsorbent to remove HF acid and an activator to assist C-F bond cleavage.
L. Kang, J. Zhang, H. Yang, J. Qian, G. Jiang, Synlett, 2021, 32, 785-789.
Sequential coupling-imination-annulation reactions of ortho-bromoarylaldehydes and terminal alkynes with ammonium acetate in the presence of a palladium catalyst under microwave irradiation gives various substituted isoquinolines, furopyridines, and thienopyridines in good yields.
D. Yang, S. Burugupalli, D. Daniel, Y. Chen, J. Org. Chem., 2012, 77, 4466-4472.
A thiolate anion promotes a transition-metal free cleavage of two carbon-sulfur bonds in 2,2′-bis(methylthio)-1,1′-biaryl derivatives. The subsequent dibenzothiophene-forming cyclization step proceeds through a concerted nucleophilic aromatic substitution (CSNAr) mechanism.
Y. Masuya, Y. Kawashima, T. Kodama, N. Chatani, M. Tobisu, Synlett, 2019, 30, 1995-1999.
An N- and S-arylation sequence of o-sulfanylanilines enables an efficient synthesis of various N-arylphenothiazines under transition-metal-free conditions.
T. Matsuzawa, T. Hosoya, S. Yoshida, Org. Lett., 2021, 23, 2347-2352.
An isothiourea-catalyzed enantioselective formal [4+3] cycloaddition of various α,β-unsaturated carboxylic acid derivatives with 2-aminothiophenols proceeds via a reversible sulfa-Michael addition to α,β-unsaturated acylammonium intermediates, followed by an enantioselective formation of a seven-membered ring. This method enables a facile and divergent synthesis of optically active 2- and 3-substituted 1,5-benzothiazepines.
Y. Fukata, K. Yao, R. Miyaiji, K. Asano, S. Matsubara, J. Org. Chem., 2017, 82, 12655-12668.