A systematic approach toward Lewis acid catalyzed inverse electron-demand Diels-Alder (IEDDA) reactions of 1,2-diazines is described. The general concept is first investigated by DFT calculations, supported by spectroscopic data, and finally proven in the experiment.

Bidentate Lewis acids were applied as catalysts for the inverse‐electron‐demand Diels–Alder (IEDDA) reaction of 1,2‐diazines. The concept of catalysis is based on the coordination of the bidentate Lewis acid to both nitrogen atoms of the 1,2‐diazine moiety, thereby reducing the electron density and lowering the energy of the LUMO. This should, according to frontier molecular orbital (FMO) theory, facilitate the cycloaddition step. This new concept was successfully applied to a variety of dienophiles and substituted phthalazine substrates. Careful investigations of the mechanism led to the isolation and characterization of key intermediates; all of which support the presented catalytic cycle.

Presented herein is a mild, facile, and efficient iron‐catalyzed synthesis of substituted allenes from propargyl carboxylates and Grignard reagents. Only 1–5 mol % of the inexpensive and environmentally benign [Fe(acac)3] at −20 °C was sufficient to afford a broad range of substituted allenes in excellent yields. The method tolerates a variety of functional groups.

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.

A domino process consisting of an inverse and a normal electron-demand Diels-Alder reaction is presented for the formation of bridged tri- and tetracyclic 1,2,3,4-tetrahydronaphthalenes catalyzed by a bidentate Lewis acid. The products were synthesized in a one-pot reaction from commercially available starting materials and contain up to six stereogenic centers. The tetrahydronaphthalenes were isolated as single diastereomers and are derivatives of phenylethylamine, which is well-known as a scaffold of amphetamine or dopamine.