Domino aziridine ring opening and Buchwald–Hartwig type coupling-cyclization by palladium catalyst

Domino ring opening/cyclization of oxiranes for synthesis of functionalized 2H-pyran-5-carboxylate

A simple method for the synthesis of functionalized 2H-pyrans via a catalytic reaction of an oxirane, an alkyne, and a malonate has been developed in which a 6-exo-dig cyclization pathway is observed. In this transformation, the attack of in situ generated copper acetylides on oxiranes formed homopropargylic alcohol intermediates which further transferred to 2H-pyrans with the help of malonates.

Synthesis of Nonracemic 1,4-Benzoxazines via Ring Opening/Cyclization of Activated Aziridines with 2-Halophenols: Formal Synthesis of Levofloxacin

Novel 3,4-dihydro-1,4-benzoxazine derivatives have been synthesized by an efficient and simple method in excellent enantio- and diastereospecificity (ee > 99%, de > 99%). The reaction proceeds via Lewis acid-catalyzed S_N2-type ring opening of activated aziridines with 2-halophenols followed by Cu(I)-catalyzed intramolecular C-N cyclization in a stepwise fashion under one-pot conditions to furnish the 3,4-dihydro-1,4-benzoxazine derivatives in excellent yields (up to 95%). The strategy offers a short and efficient synthesis to ( S)-3-methyl-1,4-benzoxazine ( S)-3v, a late stage intermediate in the synthesis of levofloxacin.

One-Pot Synthesis of Benzo[b][1,4]oxazins via Intramolecular Trapping Iminoenol

A highly atom-efficient "one-pot" protocol has been developed to construct multisubstituted 2-hydroxy-benzo[b][1,4]oxazins starting from N-(2-hydroxylaryl)enaminones. This procedure comprises a PIDA-mediated intramolecular iminoenol tautomer trapping reaction, followed by Et₃N-promoted aerobic oxidative ring construction. In particular, an O₂ molecule from air served as the oxygen source of the hydroxyl group in the titled products. This reaction proceeded smoothly at room temperature under air atmosphere and metal-free conditions.

An efficient synthesis of pyrido[1,2-a]indoles through aza-Nazarov type cyclization

Transition metal free Brønsted acid mediated synthesis of pyrido[1,2-a]indole scaffolds has been developed through aza-Nazarov type cyclization of readily available diaryl(2-pyridyl)methanol using formic acid for the synthesis of biologically and medicinally important pyrido[1,2-a]indole, indolo[1,2-a]quinoline and pyrimido[1,2-a]indole derivatives.

Selective amination of aryl chlorides catalysed by Ni(PMe3)4

C,N-coupling reactions of aryl chlorides and aryl amines catalyzed by a nickel catalyst are reported.

A rapid and modified approach for C-7 amination and amidation of 4-methyl-7-nonafluorobutylsulfonyloxy coumarins under microwave irradiation

A rapid approach for the synthesis of an array of 4-methyl-7-substituted coumarins has been developed.