Facile synthesis of 1,2,3-tricarbonyls from 1,3-dicarbonyls mediated by cerium(IV) ammonium nitrate

Synthesis of β-Carbonyl α-Iminoamides by Double Insertion of Isocyanides into Aldehydes

An unprecedented trimethylsilyl trifluoromethanesulfonate (TMSOTf)-promoted selective double insertion of isocyanides into aldehydes was developed, providing an efficient protocol for synthetically challenging β-carbonyl α-iminoamides. The given approach is applicable for a diverse selection of readily accessible aldehydes, along with isocyanides serving as essential precursors for "amide" and "imine" scaffolds. The versatile transformations of the given products were demonstrated, and the pivotal intermediates for the plausible mechanism were identified.

Recent Progress in Free Radical Transformations of Allenamides

Allenamides are special allenes, and the unique reactivity, selectivity (both stereoselective and regionally selective) and stability of allenamides have been widely studied. In this review, the development of the free radical transformation of allenamides over the last few years will be summarized. This review discusses in detail in three parts: intermolecular radical addition to C- X (X = N, S, O, Se) bonds, metal salt mediated cyclization of allenamides, and photocatalytic cyclization of allenamides. In addition, reasonable details of the mechanisms are provided for the vast majority of these transformations.

Step-Economic Total Synthesis of Melosatin A from Eugenol

An efficient and straightforward route toward the isatin-type natural product melosatin A is reported, employing a trisubstituted aniline as a key intermediate. The latter was synthesized in 4 steps and 60% overall yield from eugenol, through its regioselective nitration, sequentially followed by a Williamson methylation, an olefin cross-metathesis with 4-phenyl-1-butene and the simultaneous reduction of olefin and nitro groups. The final step, a Martinet cyclocondensation of the key aniline with diethyl 2-ketomalonate, provided the natural product with 68% yield.

Access to fused π-extended acridone derivatives through a regioselective oxidative demethylation

The oxidative demethylation of ortho-dimethoxyacridone with ceric ammonium nitrate (CAN) regioselectively furnished an ortho-quinone leaving a methoxyl group unreacted, which further condensed with aromatic ortho-diamines to afford angularly fused π-extended acridone derivatives. Crystallographic analysis reveals the distinct manner of molecular packing in the crystals according to the dimension of π-extension. The benzene at the turning point possesses a shorter outer bond and a longer inner bond, which affects molecular conjugation and results in weakened aromaticity.

Enantio- and Diastereoselective Organocatalytic Conjugate Additions of Nitroalkanes to Enone Diesters

Enantio- and diastereoselective conjugate addition reactions between nitroethane or nitropropane and enone diesters are reported. A bifunctional triaryliminophosphorane catalyzed the addition reaction with consistently excellent stereoselectivities and yields across a wide range of substrates. By the use of the gem-diester functional handle present in the adducts, local desymmetrization via diastereotopic group discrimination was demonstrated, and a polyfunctionalized lactam with three contiguous stereocenters was synthesized.

Lactols in an asymmetric aldol-desymmetrization sequence: access to tetrahydro-4H-furo[2,3-b]pyran-2-one and tetrahydro-4H-furo[2,3-b]furan-2-one derivatives

An asymmetric aldol-desymmetrization sequence was developed which provided highly efficient access to important bicyclic oxygen-containing scaffolds with multiple chiral centers and one is a quaternary stereogenic center containing a free hydroxy group. Moreover, starting from racemic precursors, the final products were obtained as two separable diastereomers by flash chromatography. Several other heterocycles could also be easily generated with this strategy.

Practical Singly and Doubly Electrophilic Aminating Agents: A New, More Sustainable Platform for Carbon-Nitrogen Bond Formation

Given the importance of amines in a large number of biologically active natural products, active pharmaceutical ingredients, agrochemicals, and functional materials, the development of efficient C-N bond-forming methods with wide substrate scope continues to be at the frontier of research in synthetic organic chemistry. Here, we present a general and fundamentally new synthetic approach for the direct, transition-metal-free preparation of symmetrical and unsymmetrical diaryl-, arylalkyl-, and dialkylamines that relies on the facile single or double addition of readily available C-nucleophiles to the nitrogen atom of bench-stable electrophilic aminating agents. Practical single and double polarity reversal (i.e., umpolung) of the nitrogen atom is achieved using sterically and electronically tunable ketomalonate-derived imines and oximes. Overall, this novel approach represents an operationally simple, scalable, and environmentally friendly alternative to transition-metal-catalyzed C-N cross-coupling methods that are currently used to access structurally diverse secondary amines.

Oxidation of β-Ketoamides: The Synthesis of Vicinal Tricarbonyl Amides

A facile and direct oxidative reaction for the synthesis of vicinal tricarbonyl amides in moderate to excellent yields (53-88%) was developed starting from readily available β-ketoamides in the presence of phenyliodine(III) bis(trifluoroacetate). The resulting products possess significant synthetic potential, making this approach a valuable addition to the group of traditional methods already available for the preparation of these molecules.

Iodosobenzene-mediated direct and efficient oxidation of β-dicarbonyls to vicinal tricarbonyls catalyzed by iron(iii) salts

The direct and efficient oxidation of β-dicarbonyls to vicinal tricarbonyl compounds has been achieved, which was mediated by PhIO and catalyzed by Fe(NO₃)₃·9H₂O under mild and environmentally friendly conditions.