Conjugate addition nitro-Mannich reaction of carbon and heteroatom nucleophiles to nitroalkenes

Triethylamine-Promoted Henry Reaction/Elimination of HNO2/Cyclization Sequence of Functionalized Nitroalkanes and 2-Oxoaldehydes: Diversity-Oriented Synthesis of Oxacycles

The triethylamine-promoted cascade Henry reaction/elimination of HNO₂/cyclization reaction of 2-oxoaldehydes with nitroalkanes bearing various remote functionalities is described. Both chiral and achiral nitroalkanes were applicable to this protocol, leading to a variety of oxacycles, such as chromenes, chromanes, cyclic hemiacetals, and polycyclic acetals. An unexpected regioselective photooxygenation occurred without sensitizer during derivatization to convert a derived diene product into a dioxetane by reaction with singlet oxygen, which provided chromen-2-one and benzaldehyde after fragmentation.

Denitrative Cross-Couplings of Nitrostyrenes

Interestingly, β-nitrostyrenes, typically bench stable compounds, are highly promising cross-coupling partners, due to their excellent availability and well understood reactivity. In this review, we report on the discovery and advancements, in the field of stereoselective, denitrative cross-couplings of β-nitrostyrenes with miscellaneous organic reagents. The rapidly expanding field offers alternative access to a broad range of functionalized alkenes, including β-alkylated styrenes, chalcones, stilbenes, cinnamic acids, and conjugated sulfones and phosphonates. The most important mechanistic pathways are briefly discussed, to familiarize readers with the elementary reactions occurring during the coupling.

A Divergent Synthetic Route to the Vallesamidine and Schizozygine Alkaloids: Total Synthesis of (+)-Vallesamidine and (+)-14,15-Dehydrostrempeliopine

The total synthesis of representative members of the schizozygine alkaloids, (+)-vallesamidine and (+)-14,15-dehydrostrempeliopine, were completed from a late-stage divergent intermediate. The synthesis took advantage of efficient nitro-group reactions with the A/B/C ring skeleton constructed concisely on a gram scale through an asymmetric Michael addition, nitro-Mannich/lactamisation, Tsuji-Trost allylation, and intramolecular C-N coupling reaction. Other key features of the synthesis are a novel [1,4] hydride transfer/Mannich-type cyclisation to build ring E and a diastereoselective ring-closing metathesis reaction to construct ring D. This approach gave access to a late-stage C14,C15 alkene divergent intermediate that could be simply transformed into (+)-vallesamidine, (+)-14,15-dehydrostrempeliopine, and potentially other schizozygine alkaloids and unnatural derivatives.

Base-Controlled Diastereoselective Synthesis of Either anti- or syn-β-Aminonitriles

Deprotonation of secondary alkane nitriles with nBuLi and addition to aryl imines gives kinetic anti-β-aminonitriles. Use of LHMDS allows reversible protonation of the reaction intermediate to give syn-β-aminonitriles. The pure diastereosiomers can be isolated in good yields, and the mechanism was elucidated.

Silver-catalyzed synthesis of 2-arylvinylphosphonates by cross-coupling of β-nitrostyrenes with H-phosphites

An efficient protocol for stereoselective synthesis of vinylphosphonates has been developed via AgNO₃-catalyzed cross-coupling of β-nitrostyrenes with dialkyl H-phosphites under mild conditions.

On-water magnetic NiFe2O4 nanoparticle-catalyzed Michael additions of active methylene compounds, aromatic/aliphatic amines, alcohols and thiols to conjugated alkenes

Here, we have demonstrated Michael addition of active methylene compounds, aromatic/aliphatic amines, thiols and alcohols to conjugated alkenes using magnetic nano-NiFe₂O₄ as reusable catalyst in water.

Reductive conjugate addition nitro-Mannich route for the stereoselective synthesis of 1,2,3,4-tetrahydroquinoxalines

A reductive conjugate addition nitro-Mannich reaction controls diastereoselectivity in a rapid entry to a diverse array of 1,2,3,4-tetrahydroquinoxalines in high yield.

Cinchona alkaloid-based chiral catalysts act as highly efficient multifunctional organocatalysts for the asymmetric conjugate addition of malonates to nitroolefins

New pentaerythritol tetrabromide-based chiral quaternary ammonium salts acting as organocatalysts (7a and 7b) have been prepared and used as organocatalysts for enantioselective Michael addition reactions between various nitroolefins and Michael donors (malonates) under mild reaction conditions, such as lower concentration of base and catalyst and room temperature, with very good chemical yields (up to 97%) and ee's (up to 99%).

Manganese(iii)-mediated alkenyl Csp2–P bond formation from the reaction of β-nitrostyrenes with dialkyl phosphites

Mn(OAc)₃-mediated tandem phosphonyl radical addition to β-nitrostyrenes followed by denitration to form (E)-2-alkenyl phosphonates is described.