An Inverse Electron Demand Azo-Diels–Alder Reaction of o-Quinone Methides and Imino Ethers: Synthesis of Benzocondensed 1,3-Oxazines

Abstract

We have studied the reactions of o-quinone methide precursors with imino ethers. The reaction provides a versatile route to substituted 1,3-benzoxazines. The proposed reaction mechanism involves the generation of the o-quinone methide intermediates, imino-Diels-Alder reaction, and elimination. This cascade process is a rare example of the participation of imino ethers as dienophiles.

Electrochemical Intramolecular Dehydrogenative Coupling of N‐Benzyl(thio)amides: A Direct and Facile Synthesis of 4H‐1,3‐Benzoxazines and 4H‐1,3‐Benzothiazines

“…The fluoride substrate could also provide the desired product in moderate yield, but the chloride substrate failed (Table , 2i , 2i′ ). This electrosynthetic method was also compatible for the synthesis of 1 H ‐naphtho[1,2‐ e ][1,3]oxazine, which represents the core structure of a serie of compounds exhibiting antifungal and antimicarobial activity (Table , 2j ) . Benzylic mono‐substituted or gem‐substituted N ‐benzyl amides also furnished the corresponding products in satisfied yields (Table , 2k – p ).…”

“…2,4,4‐Triphenyl‐4 H ‐benzo[ e ][1,3]oxazine (2p): [20a] White solid, 55 mg (76 % yield). 1 H NMR (600 MHz, CDCl 3 ): δ = 8.20 (d, J = 7.4 Hz, 2 H), 7.48 (t, J = 7.3 Hz, 1 H), 7.43 (t, J = 7.5 Hz, 2 H), 7.34–7.27 (m, 5 H), 7.25–7.21 (m, 6 H), 7.19 (d, J = 8.1 Hz, 1 H), 7.10 (t, J = 7.5 Hz, 1 H), 6.90 (d, J = 6.7 Hz, 1 H) ppm.…”

Machine learning reaction barriers in low data regimes: a horizontal and diagonal transfer learning approach

“…A diverse selection of Diels–Alder reactions (Fig. S1†) were enumerated using prevalent motifs throughout the literature, including a variety of intra/intermolecular and homo/hetero-Diels–Alder reactions, 43–53 as well as additional pericyclic reactions ( e.g. , tetrazine-based reactions).…”

“…A diverse selection of Diels-Alder reactions (Fig. S1 †) were enumerated using prevalent motifs throughout the literature, including a variety of intra/intermolecular and homo/hetero-Diels-Alder reactions, [43][44][45][46][47][48][49][50][51][52][53] as well as additional pericyclic reactions (e.g., tetrazine-based reactions). 54,55 Enumerations were performed using Schrödinger's Custom R-Group Enumeration 56 and all subsequent reactant and transition state (TS) structures conformationally searched using Schrödinger's MacroModel (version 12.7) 57,58 with the OPLS3e forceeld.…”

Synthesis, Kinetics, Reaction Mechanism and Biological Activity Studies of Novel 1, 3-Oxazine Compound

“…Oxazine compounds have been found to have in vitro anti-inflammatory activity using the bovine serum albumin with protease method, and ZANCO Journal of Pure and Applied Sciences 2023 their antioxidant activity was assessed using the diphenyl picryl hydrazide with nitric oxide method. Therefore, it is important to discover new classes of chemicals with effective mechanisms (Osipov et al, 2018, Chaitra and Rohini, 2018, Zinad et al, 2020, Doherty et al, 1995, Ananthula et al, 2014, Sabre, 2022, D'Andrea et al, 2005. The kinetics of the 2methyl-5,6-dihydro-4H-1,3-oxazine (MeOZI) isomerization polymerization initiated by methyl tosylate (MeOTs) and methyl iodide (MeI) in nitrobenzene as a solvent have been described by Saegusa and colleagues.…”