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.
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.
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.