Multicomponent Reaction for the Synthesis of 5,6-Dihydropyrrolo[2,1-a]isoquinolines.

A multicomponent reaction between isatin, tetrahydroisoquinoline, and terminal alkyne in the presence of benzoic acid for the synthesis of N-(substituted-2-(2-phenyl-5,6-dihydropyrrolo[2,1-a]isoquinolin-3-yl)phenyl)-3,4-dihydroisoquinoline-2(1H)-carboxamides is described. This three-component reaction proceeds via sequential formation of spirooxindole, generation of isocyanate functionality via cleavage of the C2-C3 bond in the isatin subunit of spirooxindole, and addition of the second molecule of tetrahydroisoquinoline to the isocyanate group to offer title compounds. Expansion of the protocol to four-component by including an additional primary amine affords 1-substituted-3-(2-(2-phenyl-5,6-dihydropyrrolo[2,1-a]isoquinolin-3-yl)phenyl)urea in low to moderate yields. However, the reaction of intermediate spirooxindole with tetrahydroisoquinoline or any primary or secondary amine produced the title compound in excellent yields.

Dehydrative Transformation of Spirooxindoles to Pyrido[2,3-b]indoles via POCl3.

A two-step one-pot efficient synthesis of pyrido[2,3-b]indoles via reaction between isatin, α-amino acid, and dipolarophile has been developed. The initial 1,3-dipolar cycloaddition between the reactants that is performed in the presence of either CuI or methanol results in spirooxindoles that undergo POCl3-mediated intramolecular dehydrative transformation to afford the title compounds.

Transformations of alkynes to carboxylic acids and their derivatives via C[triple bond, length as m-dash]C bond cleavage.

Alkynes are building blocks of high synthetic value and their usefulness as precursors to many chemical and biological systems is widely established. Amongst several transformations of alkynes, cleavage of the C[triple bond, length as m-dash]C bond for obtaining diverse compounds is considered to be important. This review, in particular, comprehensively assimilates the transformations of alkynes to carboxylic acids including esters, amides and nitriles resulting from the cleavage of the C[triple bond, length as m-dash]C bond either under the influence of a metal catalyst or via a metal-free approach.

Pd(OAc)2-catalysed regioselective alkoxylation of aryl (ß-carbolin-1-yl)methanones via ß-carboline directed ortho-C(sp(2))-H activation of an aryl ring.

Synthesis of (2-alkoxyphenyl)(9H-pyrido[3,4-b]indol-1-yl)methanone via Pd(OAc)2-catalyzed regioselective alkoxylation of aryl (ß-carbolin-1-yl) methanones employing ß-carboline directed ortho-C(sp(2))-H activation of an aryl ring under oxidative conditions is described.

Synthesis of 3,4,5-Trisubstituted Isoxazoles from Morita-Baylis-Hillman Acetates by an NaNO2 /I2 -Mediated Domino Reaction.

An efficient NaNO2 /I2 -mediated one-pot transformation of Morita-Baylis-Hillman (MBH) acetates into alkyl 3-nitro-5-(aryl/alkyl)isoxazole-4-carboxylates is described. In a cascade event, initial Michael addition of NaNO2 to the MBH acetate furnishes the allylnitro intermediate which undergoes I2 -catalyzed oxidative α-CH nitration of the nitromethyl subunit followed by [3+2] cycloaddition to afford the title compounds. Structural elaborations of these highly substituted isoxazoles by SN Ar reactions and hydrogenolysis allows access to useful products.