Intramolecular Diels–Alder Reactions of α-Bromostyrene-Functionalized Unsaturated Carboxamides

Abstract

Intramolecular cycloaddition reactions of α-bromostyrene-functionalized amides of monomethyl fumarate were investigated. The reaction of the amides with Et3N in toluene at 110 °C gave 1,4-dihydronaphthalenes. The 1,4-dihydronaphthalenes may be produced via the intramolecular Diels–Alder reaction, proton transfer, and dehydrobromination by a base, along with CC bond isomerization by proton transfer. The reaction of amide derivatives with halogen on a benzene ring and alkali metal carbonates in toluene at 110 °C gave naphthalene derivatives directly. Dehydrogenation of various 1,4-dihydronaphthalenes with cesium or rubidium carbonate in toluene at 110 °C gave naphthalene derivatives. The retardation by TEMPO, acceleration by air for some substrates, and density functional theory calculations suggest a radical mechanism caused by intervention of molecular oxygen.

Intramolecular cyclization reactions of arylpropargyl amides of electron-deficient α,β-alkenyl carboxylates and related compounds

“…1 H NMR spectra of 4a , 4g , 4h , 4i , 4j , and 4l were consistent with those previously reported. 2…”

“…The 1 H NMR spectra of 4b were consistent with those previously reported. 2 4d: (0.5 mmol scale, 88 mg, 47%); R f = 0.3 (hexane-ether = 1 : 4); yellow crystals; mp 218-219 °C (hexane-EtOAc); Procedure for Scheme 11. To a mixture of EtOH (1.2 mL), AcOH (1.2 mL), H 2 O (0.6 ml) and 1 drop of conc.…”

“…1 Recently, we have reported intramolecular Diels–Alder reactions of α-bromo styrene substituted fumarate amides to give pyrrolidine-fused heterocycles, benz[ f ]isoindolines. 2 The α-bromo styrene moiety was used as a surrogate of an aryl alkyne. In the intramolecular Diels–Alder reactions of styrene derivatives, aryl alkynes have often been used as dienophiles.…”

Recent Advances in Design and Synthesis of 1,3-Thiaselenolane and 1,3-Thiaselenole Derivatives

“…The reaction was carried out in methanol at 0 • C. For example, alkyl 3-[(1,3-thiaselenol-2-ylmethyl)selanyl]-2-propenoates 13a (Z/E = 94/6) and 13b (Z/E = 93/7) were obtained in a regio-and stereoselective fashion in 94% and 90% yields, respectively (Scheme 7) [77]. It is known that metal carbonates can be used not only as dehydrobrominating but also as catalytic reagents [80][81][82][83][84]. In this case, six-membered products 15a-d were rearranged into more stable thermodynamic five-membered products 16a-d under the action of lithium or potassium carbonate.…”