Lewis acid-catalyzed [4 + 2] cycloaddition of donor–acceptor cyclobutanes with iminooxindoles: access to spiro[piperidine-3,2′-oxindoles]

Abstract

A Lewis acid-catalyzed [4 + 2] cycloaddition reaction from D–A cyclobutanes and iminooxindoles, providing the corresponding spiro[piperidine-3,2′-oxindoles] under mild conditions.

Accessing spiropiperidines from dihydropyridones through tandem triflation–allylation and ring-closing metathesis (RCM)

“…[10][11][12] On the other hand, the piperidine ring is a common structural motif present in natural and/or synthetic products of pharmaceutical importance, and within this class of saturated nitrogen heterocycles, the spiropiperidine moiety, which is capable of exploring and spanning a large binding pocket due to its rigidly defined structure, has been considered a "privileged structure" and thus has become a sought-after motif for medicinal chemists. [13][14][15][16][17][18][19][20][21] (−)-Histrionicotoxin, a potent noncompetitive antagonist of nicotinic acetylcholine receptors, 22 (+)-nitramine 23 and ibutamoren, a potent agonist of the ghrelin receptor, 24 are examples of synthetic or natural biologically active spiropiperidines (Fig. 1).…”