Competitive Formation of β‐Enaminones and 3‐Amino‐2(5H)‐furanones from the Isoxazolidine System: A Combined Synthetic and Quantum Chemical Study

Abstract

Treatment of 3‐alkoxycarbonyl‐4‐acyl‐ or 3,4‐dialkoxycarbonyl‐substituted isoxazolidines with a mild base, such as tetrabutylammonium fluoride, affords β‐enaminones and/or 3‐methylamino‐2(5H)‐furanones according to the nature of the substituents at C4 and C5. Two alternative mechanisms (lactonization and retro‐aldolization) have been rationalized by DFT quantum chemical methods. Any realistic theoretical modeling requires the explicit inclusion of countercation and solvent effects.

5-(3-Phosphonated 1H-1,2,3-triazol-4-yl)isoxazolidines: synthesis, DFT studies and biological properties

“…In particular, the 1 The observed stereochemistry is in deep contrast with the precedent results reported for the cycloaddition reactions of this nitrone with various electron-rich, electron-poor and conjugative dipolarophiles, in which the trans adducts are the major stereoisomers. 8,30 Then, to rationalize the observed high regio-and stereoselectivity, a computational study at DFT level [31][32][33][34] was performed using the M062X/6-31G(d,p) calculations.…”

Chalcones as Versatile Synthons for the Synthesis of 5- and 6-membered Nitrogen Heterocycles

“…Four isomers were generated in the reaction of chalcone with Cethoxycarbonyl-N-methylnitrone. Using aluminum tris(2,6diphenylphenoxide) (ATPH) as catalyst increased the yields obtained but the low regio-and stereoselectivities remains [157]. The C-diethoxyphosphoryl-N-methylnitrone 5 was used by Piotrowska et al in the 1,3-dipolar cycloaddition reaction with chalcones to obtain a new series of four isomeric isoxazolidin-3-yl-3phosphonates (Scheme 17).…”

A Highly Efficient and Stereoselective Cycloaddition of Nitrones to N-Vinylpyrroles

“…The basic treatment of isoxazolidines suitably activated at the 3-position of the ring has been exploited for a synthetic approach to 3-(alkylamino)furan-2(5H)-ones, versatile synthons for β-lactams 18,19 and (or) β-enaminones. 20 Treatment of isoxazolidines 7c,d with sodium hydride or tetrabutylammonium fluoride led to the formation of com-…”