1515871-22-3Relevant academic research and scientific papers
Polycyclic Ring Formation Using Bis-diazolactams for Cascade Stitching
Bonderoff, Sara A.,Padwa, Albert
, p. 642 - 651 (2017)
The chemoselective reaction of donor/acceptor (D/A) and acceptor/acceptor (A/A) diazo moieties in the same molecule was examined using 3-diazo-1-(ethyl 2-diazomalonyl)indolin-2-one under rhodium(II) catalysis. The metallo carbenoid derived from the D/A diazo group is preferentially formed and undergoes selective CH, NH, and OH insertion reactions, cyclopropanation, cyclopropenation, sulfur ylide formation/2,3-sigmatropic rearrangement, as well as nitrogen ylide formation followed by azetidine ring expansion. The initial reaction can be paired with a subsequent tandem cascade sequence involving dipole formation/cycloaddition in either an intra- or intermolecular sense to generate polycyclic N-heterocycles in one pot, with the formation up to three new rings in a single operation. Excellent diastereoselectivity was observed in the intramolecular cycloaddition reaction producing 5 to 7-membered rings.
Model studies directed toward the alkaloid mersicarpine utilizing a Rh(II)-catalyzed insertion/cycloaddition sequence
Li, Hao,Bonderoff, Sara A.,Cheng, Bo,Padwa, Albert
, p. 392 - 400 (2014/01/17)
Model studies dealing with the rhodium(II)-catalyzed carbenoid insertion/cyclization/cycloaddition cascade of several α-diazo dihydroindolinones have been carried out as an approach to the alkaloid mersicarpine. The cascade reaction of α-diazo dihydroindolinone 21 proceeded in high yield with excellent diastereoselectivity to give cycloadduct 22, which possesses the required stereochemistry of the two adjacent quaternary carbon centers present in mersicarpine. The overall reaction enabled the rapid assemblage of a polycyclic ring system that contains three new stereocenters and three continuous quaternary carbons in a single operation in high yield with excellent diastereoselectivity. The 3-indolinone derivative 36 was eventually formed from cycloadduct 22 by an acid-induced hydrolysis of 22 to give 23, which was subsequently converted in several steps to 36. The synthesis of this compound constitutes a successful construction of the tricyclic core of mersicarpine. Reduction of the nitrile group of 36 followed by a subsequent reductive cyclization/ring-opening aromatization cascade, as was found to occur with the related compound 29, will be employed for an eventual synthesis of demethylmersicarpine.
