Polarity-Reversible Conjugate Addition Tuned by Remote Electronic Effects

Novel synthesis of fused spiro piperidone-cyclopropanes from cyclopropyl amides and electron-deficient alkenes

We report here that a series of bridged O,O-ketal fused spiro piperidone-cyclopropane derivatives 3 can be constructed with excellent yields and good diastereoselectivity by the one-pot reaction of 1-acylcyclopropanecarboxamides 1 with electron-deficient alkene 2a (EWG = CHO) via the domino process involving [4 + 2] annulation/intermolecular electrophilic addition/intramolecular cyclization. Furthermore, reactions of 1 with 2b/2c (EWG = CN, COOMe), leading to spiro piperidone-cyclopropane derivatives 4 or 5 by base catalyst selection, were also presented.

Synthesis of Tetramic Acid Derivatives via a Tandem Umpolung Alkylation/Reduction/Cyclization Reaction of γ-Hydrazono β-Ketoester

An efficient method for the one-pot synthesis of tetramic acid derivatives was developed utilizing tandem umpolung N-alkylation/reduction/cyclization of γ-hydrazono β-ketoester. By using this reaction as a key step, the total synthesis of the 3-spiro 7-hydroxamic acid tetralin which possesses an HDAC inhibitory activity was also achieved.

Construction of piperidine-2,4-dione-type azaheterocycles and their application in modern drug development and natural product synthesis

The review surveys the existing routes to piperidine-2,4-dione-type heterocycles including derivatives with the most vital types of biological activity. This heterocyclic platform is ideal for the construction of modern drugs and natural products.

Ag NPs decorated on a COF in the presence of DBU as an efficient catalytic system for the synthesis of tetramic acids via CO2 fixation into propargylic amines at atmospheric pressure

Ag NPs are decorated at the surface of a COF material TpPa-1 and the resulting Ag@TpPa-1 catalyzes efficiently for the synthesis of tetramic acids from a variety of propargylic amines using CO₂ as reagent.

Intramolecular macrolactonization, photophysical and biological studies of new class of polycyclic pyrrole derivatives

Herein, we report an efficient synthesis of N-substituted pyrrole derivatives and their application to construct macrocyclic oxazocinone.

Novel method of tetramic acid synthesis: silver-catalyzed carbon dioxide incorporation into propargylic amine and intramolecular rearrangement

Tetramic acid derivatives have been studied as biologically active heterocycle structures for pharmaceutical or agricultural chemicals. Conventional preparative approaches often require highly functionalized starting materials and harsh heating conditions in basic media. The present report provides a conceptually new synthetic strategy for the synthesis of tetramic acid derivatives from easily available propargylic amines and carbon dioxide with a silver salt and DBU under mild reaction conditions.

Aerobic copper-catalyzed oxidative [6C+1C] annulation: an efficient route to seven-membered carbocycles

A copper-catalyzed aerobic tandem Michael addition–intramolecular radical cyclization–benzyl C(sp³)–H bond oxidation reaction of dicinnamoyl ketene dithioacetals and ethyl cyanoacetate was developed for the diastereoselective synthesis of seven-membered carbocycles.

Recent developments of ketene dithioacetal chemistry

Ketene dithioacetals are versatile intermediates in organic synthesis. Extensive research, since the last decade, has given rise to new prospects in their chemistry. The objective of this review is twofold: first, to highlight the new prospects in the chemistry of functionalized ketene dithioacetals, and second, to provide an intrinsic link between ketene dithioacetal groups and a variety of other functional groups, which has brought out many new facts that will assist in future designs.

α(δ')-Michael addition of alkyl amines to dimethyl (E)-hex-2-en-4-ynedioate: synthesis of α,β-dehydroamino acid derivatives

The direct nucleophilic addition of alkyl amines to the α(δ')-carbon atom of dimethyl (E)-hex-2-en-4-ynedioate to generate α,β-dehydroamino acid derivatives is reported. Herein, we have studied the reactivity of various primary and secondary alkyl amines in the α-selective nucleophilic conjugate addition to conjugated dimethyl (E)-hex-2-en-4-ynedioate. The reaction with primary alkyl amines gives only the (2E,4E)-stereoisomer, while that with secondary alkyl amines gives the (2E,4E) and (2Z,4E)-stereoisomers of dimethyl (2-alkylamino)-muconic ester.

Mechanism study of the intramolecular anti-Michael addition of N-alkylfurylacrylacetamides

The mechanism of the intramolecular nucleophilic addition of N-alkylfurylacrylacetamides is investigated by density functional theory calculations. Three possible reaction pathways have been considered based on possible conformations of the same reactant, which undergoes three stages, including hydrogen elimination by the base NaH, followed by the nucleophilic addition of N(-) on C(α) (C(β)) via an anti-Michael (Michael) mechanism, and then proton transfer affords the final product Pr-5 (Pr-6). The pathway corresponding to the reactant with the most stable conformation is found to be the most favorable one. The rate-determining step of the intramolecular nucleophilic addition is the nucleophilic addition of N(-) on C(α) (C(β)) featuring a cyclic ring transition state. Solvent effects are considered at the B3LYP/6-31G(d,p) level in solvent DMSO, and the results suggest that the relative reaction trends are consistent with the gas-phase reaction. Furthermore, the difference of the energy barriers explains the origin of the regioselectivity of the experiment. Finally, the effects of the substituent on N1 and C(β) to the regioselectivity have been discussed.