Benzoic Acid Catalyzed Annulations of α-Amino Acids and Aromatic Aldehydes Containing an ortho-Michael Acceptor: Access to 2,5-Dihydro-1H-benzo[c]azepines and 10,11-Dihydro-5H-benzo[e]pyrrolo[1,2-a]azepines

Microwave-assisted decarboxylative reactions: advanced strategies for sustainable organic synthesis

Recent advances in the microwave-assisted decarboxylative reactions of carboxylic acids and their derivatives, including transition-metal-catalyzed and metal-free approaches, are summarized.

One-pot three-component reaction of p-quinone monoacetals, l-proline and naphthols to afford N-aryl-2-arylpyrrolidines

A one-pot three-component reaction of p-quinone monoacetals (or p-quinol ethers), l-proline and naphthols is developed for the synthesis of N-aryl-2-arylpyrrolidines under mild conditions with high chemo- and regioselectivity.

Traceless Redox-Annulations of Alicyclic Amines

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox-neutral annulations with ortho-(nitromethyl)benzaldehyde. Benzoic acid acts as a promoter in these reactions, which involve concurrent amine α-C-H bond and N-H bond functionalization. Subsequent removal of the nitro group provides access to tetrahydroprotoberberines not accessible via typical redox-annulations. Also reported are decarboxylative annulations of ortho-(nitromethyl)benzaldehyde with proline and pipecolic acid.

Three-Component Reactions of α-Amino Acids, p-Quinone Monoacetals, and Diarylphosphine Oxides to Selectively Afford 3-(Diarylphosphinyl)anilides and N-Aryl-2-diarylphosphinylpyrrolidines

The three-component reactions of α-amino acids, p-quinone monoacetals (or p-quinol ethers), and diarylphosphine oxides have been developed for the synthesis of 3-(diarylphosphinyl) anilides and N-aryl-2-diarylphosphinylpyrrolidines. The transformations may involve the in situ generation of conjugated azomethine ylides or 2-azaallyl anion species from the reaction of α-amino acids and p-quinone monoacetals, which are further trapped by diarylphosphine oxides.

Redox-Annulations of Cyclic Amines with ortho-Cyanomethylbenzaldehydes

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox-neutral annulations with ortho-cyanomethylbenzaldehydes. These amine α-C-H bond functionalization reactions are promoted by acetic acid. The resulting β-aminonitriles can be converted to the corresponding β-aminoalcohols in diastereoselective fashion.

Synthesis of benzoazepine derivatives via Rh(iii)-catalyzed inert C(sp2)–H functionalization and [4 + 3] annulation

A novel synthesis of benzoazepine derivatives via Rh(iii)-catalyzed inert C(sp²)–H bond functionalization and [4 + 3] annulation is presented.

An intramolecular Heck reaction of enol ethers involving β-alkoxyl elimination followed by the β-hydride elimination process: access to (Z)-ortho-formyl/keto-cinnamates

A highly regio- and stereoselective intramolecular Heck reaction of enol ethers involving β-alkoxyl elimination followed by the β-hydride elimination process has been developed.

Redox-Annulations of Cyclic Amines with 2-(2-Oxoethyl)malonates

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox-neutral annulations with 2-(2-oxoethyl)malonates in the presence of catalytic amounts of benzoic acid. These reactions install a fully saturated five-membered ring and provide access to structures closely related to the natural products crispine A and harmicine.

Decarboxylative Annulation of α-Amino Acids with β-Ketoaldehydes

Indolizidine and quinolizidine derivatives are readily assembled from l-proline or (±)-pipecolic acid and β-ketoaldehydes via a decarboxylative annulation process. These reactions are promoted by acetic acid and involve azomethine ylides as reactive intermediates.

Acetic Acid Promoted Redox Annulations with Dual C-H Functionalization

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox-neutral annulations with 2-alkylquinoline-3-carbaldehydes as well as the corresponding 4-alkyl isomers and pyridine analogues. These processes involve dual C-H bond functionalization. Acetic acid is used as a cosolvent and acts as the sole promoter of these transformations.

Decarboxylative Annulation of α-Amino Acids with γ-Nitroaldehydes

Indolizidine and quinolizidine derivatives are readily assembled from proline or pipecolic acid and γ-nitroaldehydes by means of a decarboxylative annulation process. These reactions are promoted by simple acetic acid and involve azomethine ylides as reactive intermediates. The method was applied to the synthesis of an epiquinamide analog.

An Ugi Reaction Incorporating a Redox-Neutral Amine C-H Functionalization Step

Pyrrolidine and 1,2,3,4-tetrahydroisoquinoline (THIQ) undergo redox-neutral α-amidation with concurrent N-alkylation upon reaction with aromatic aldehydes and isocyanides. Reactions are promoted by acetic acid and represent a new variant of the Ugi reaction.

Metal-free synthesis of quinazolinones without any additives in water

Here we report that an excess amount of aldehyde, in particular, aliphatic aldehyde, without any additives, efficiently facilitates the oxidation of aminal intermediates to quinazolinones in pure water.