Diazo Tetramic Acids Provide Access to Natural-Like Spirocyclic Δ^α,β-Butenolides through Rh(II)-Catalyzed O–H Insertion/Base-Promoted Cyclization

Abstract

3-Diazotetramic acids were found to be valid substrates for the recently discovered approach toward natural-like Δα,β-spirobutenolides via Rh(II)-catalyzed O–H insertion into propiolic acids followed by base-promoted intramolecular Michael addition. The target Δα,β-spirobutenolides were obtained in generally high yields and, in the case of chiral 5-monosubstituted 3-diazotetramic acids, high diastereoselectivity. The synthesis of Δα,β-spirobutenolides that we report here was virtually insensitive to the structure of the propiolic acids though it was somewhat sensitive to the structure of the 3-diazotetramic acids, thereby demonstrating quite a large scope. Thus, a new class of α-diazocarbonyl compounds suitable for the realization of the approach outlined above was identified.

Access to 2-Oxoazetidine-3-carboxylic Acids Derivatives via Thermal Microwave-Assisted Wolff Rearrangement of 3-Diazotetramic Acids in the Presence of Nucleophiles

“…Diazo tetramic derivatives 1 are available in a wide variety using the techniques described previously. [31] The conditions for their thermal decomposition were tested in a previous 4 study. [3] The reaction requires rather severe heating under microwave irradiation (200 °C, chlorobenzene, sealed vial), ensuring complete conversion of the diazo compound in a rather short time.…”

Theoretical investigation on diastereoselective [2+2] cycloaddition and Pd-catalyzed enantioselective [3+2] cycloaddition for synthesis of cis-β-lactam and exo-furobenzopyranone

“…Many advantages have been shown for Wolff rearrangement under microwave irradiation in ring expansion of aziridine [21]. Furthermore, 3-diazotetramic acid has been successfully involved in approach toward Δα,β-spirobutenolide via Rh(II)-catalyzed O-H insertion into propiolic acid and Rh(II)-catalyzed condensation with nitriles delivering compound bearing a hitherto polysubstituted oxazole [22,23]. A new breakthrough was Dar'in's Wolff rearrangement/Staudinger [2+2] cycloaddition cascade to access spiro bis-β-lactam involving 3-diazotetramic acid and imine [24].…”

Synthesis of fused tetramate-oxazolidine and -imidazolidine derivatives and their antibacterial activity

“…The tetramate ( pyrrolidine-2,4-dione) system occurs as the central scaffold in natural products with diverse bioactivity, 1,2 and is increasingly important as a synthetic skeleton in its own right. 3 Bicyclic derivatives may be accessed by a highly chemo-, diastereo-and enantioselective Dieckmann cyclisation of oxazolidine/thiazolidine templates 2a-g derived from hydroxyalkyl-and thioalkyl side chain amino acids (serine 1a, threonine 1b, allo-threonine 1c, cysteine 1d, or threo 1e and allophenylserines 1f, Scheme 1). 4,5 Of importance is the identity of the aldehyde which is used to condense the amino acids to form the oxazolidine/thiazolidine heterocycle, which has generally been limited to pivaldehyde; this aldehyde gives a relatively stable oxazolidine/thiazolidine template 2a-g, in which the bulky t-butyl group favours the most stable ring form in a ring-chain tautomeric equilibrium, and plays a significant role in the control of a subsequent diastereoselective N-acylation reaction and also directs the mode of the Dieckmann cyclisation towards bicyclic tetramates.…”