Indium(III)-Catalyzed Benzannulation of 3-Formyl-4-pyrones with Terminal Aryl Alkynes: Regioselective Synthesis of Functionalized Salicylaldehydes with ortho-Terphenyl Frameworks.

An effective and unprecedented In(III)-catalyzed [4 + 2] benzannulation of 3-formyl-4-pyrones with simple arylacetylenes is reported, which enables their conversion into structurally diverse salicylaldehyde-bearing ortho-terphenyl frameworks. This transformation is achieved via an In(III)-catalyzed C-O bond extrusion and proceeds without the requirement for an external oxidant. This protocol directly provides aromatic compounds from 4-pyrones. Isotopic substitution experiments suggest that the reaction proceeds via a stepwise sequence involving the addition of an alkyne to the pyran moiety followed by cyclization, oxidation, decarboxylation, and aromatization. The synthetic utility of this protocol is demonstrated by the transformation of the obtained product into molecules with bisindole, chromene, and oxime moieties.

Newly synthesized 3-sulfenylindole derivatives from 4-hydroxydithiocoumarin using an oxidative cross dehydrogenative coupling reaction (OCDCR): potential lead molecules for antiproliferative activity.

An expedient and efficient synthetic method was developed for the oxidative cross dehydrogenative coupling reaction between 4-hydroxydithiocoumarin and indole at the C-3 position regio-selectively using a combination of 10 mol% molecular iodine and TBHP in the presence of 10 mol% CuBr2 as an additive at room temperature. Mild reaction conditions, good yields and a broad substrate scope are some of the salient features of the present protocol. Additionally, the synthesized 3-sulfenylindoles derived from 4-hydroxydithiocoumarin were converted into biologically active sulfone derivatives. Interestingly, some of the compounds exhibit anti-cell proliferative activity on breast cancer (MCF-7) cells due to reactive oxygen species (ROS) mediated cell damage.

Electronic effect of substituents on anilines favors 1,4-addition to trans-ß-nitrostyrenes: access to N-substituted 3-arylindoles and 3-arylindoles.

A simple and an efficient method for the regioselective synthesis of N-alkyl/aryl/H 3-arylindole derivatives from N-substituted anilines and trans-ß-nitrostyrenes has been described using 10 mol% of bismuth(iii) triflate as a catalyst in acetonitrile at 80 °C. The present protocol profits from the formation of new C-C and C-N bonds, broad substrate scope and moderate to good yields.

An oxidative cross-coupling reaction of 4-hydroxydithiocoumarin and amines/thiols using a combination of I2 and TBHP: access to lead molecules for biomedical applications.

A metal-free I2/TBHP induced highly atom economic and operationally simple oxidative cross-coupling reaction has been developed for the direct synthesis of sulfenamides/sulfanes/disulfides from the reaction of 4-hydroxydithiocoumarin and amines/thiols. The novelties of the present protocol are unprecedented S-C bond formation in addition to S-N and S-S bonds, shorter reaction time, mild and environmentally benign reaction conditions, functional group tolerance and moderate to excellent yields. Moreover, the four newly synthesized compounds namely 4q, 6d, 6e and 7a exhibit anti-proliferative activity against the breast cancer cell line MCF7, and may be lead molecules for future drug development.

K2CO3 catalyzed regioselective synthesis of thieno[2,3-b]thiochromen-4-one oximes: access to the corresponding amine and nitroso derivatives.

An unprecedented and efficient method for the synthesis of useful thieno[2,3-b]thiochromen-4-one oximes is accomplished via a thio[3 + 2] cyclization reaction of 4-hydroxydithiocoumarins and trans-ß-nitrostyrenes in the presence of 10 mol% K2CO3 in ethanol under reflux conditions. Furthermore, hitherto, these precursors were converted into the corresponding 2-amino thieno[2,3-b]thiochromen-4-one and 2-nitroso thieno[2,3-b]thiochromen-4-one derivatives respectively. The salient features of the present protocol are mild reaction conditions, shorter reaction times, good yields and unexpected formation of C-C and C-S bonds in a regioselective manner.