Domino Inverse Electron-Demand Diels–Alder/Cyclopropanation Reaction of Diazines Catalyzed by a Bidentate Lewis Acid

Abstract

A domino inverse electron-demand Diels-Alder (IEDDA)/cyclopropanation reaction of diazines was discovered by applying electron-rich furans in the bidentate Lewis acid catalyzed IEDDA reaction. This process produces benzonorcaradienes in excellent yields with a low loading of a bidentate Lewis acid catalyst of 2 to 5 mol %. We demonstrate the broad applicability by 20 examples with different dienophiles and a variety of dienes. A detailed mechanism is proposed supported by DFT calculations.

Recent developments in and perspectives on three-coordinate boron materials: a bright future

“…146–156 The 9,10-diboraanthracenes have been successfully applied as catalysts for dihydrogen activation 157 and the inverse-electron-demand Diels–Alder reaction. 158,159 When the boron atoms are protected by bulky substituents, such as 9-anthrancenyl or 2-mesityl, the diboraanthracenes 34–36 are stable in air for several hours or days, and could be isolated following chromatography on a silica column. However, degradation was observed in dilute solutions (10 –5 M) of 37 during photophysical measurements.…”

Bis‐Boron Compounds in Catalysis: Bidentate and Bifunctional Activation

“…As described earlier, dihydrofurans are suitable dienophiles for bidentate Lewis acid catalyzed IEDDA reactions, but also electron‐rich oxyfurans are capable starting materials. In 2012 we reported a domino process, in which the reactive o ‐quinodimethane‐like dihydronapthalene intermediate was utilized in a cyclopropanation reaction (Scheme ) . The reaction led to benzonorcaradienes 34 , which are cyclopropane annulated 1,2‐dihydronaphthalene scaffolds found, for example, in natural products .…”

“… Selected examples of the catalyzed domino IEDDA/cyclopropanation reaction using bidentate Lewis acid 10 as catalyst …”

Investigation of the reaction mechanism of [4 + 2] cyclization of 2,3 dimethylbuta-1,3-diene to methylacrylate using the Michaelis-Menten equation

“…The Diels-Alder reactions may actually take place according to a two-step mechanism [8][9][10][11][12].…”

“…On the other hand, reactions e.g. of 3-nitropyridine with 1-methoxy-3-trimethoxysillylbuta-1,3-diene [9], 4,6-dinitrobenzofuroxan with 1-trimethylsilyloxybuta-1,3-diene [10], aryl-substituted 1,2,4-triazines with 2-cyclopropylidene-1,3-dimethylimidazolidine [11] and 1,1,1-trifluor-3-nitroprop-2-ene derivatives with enamines [12] take place according to a two-step, zwitterionic mechanism.…”