Development of a bidentate lewis acid catalyzed inverse electron demand diels-alder reaction of 1,2-diazines for the synthesis of substituted arenes

The efficient use of resources, as well as the minimization of waste and production costs is now more import than ever. Therefore, the development of new catalytic synthetic methods is an integral part of the research in the field of Organic Chemistry. Herein presented is a novel and very successful principle of activation of 1,2-diazines trough a bidentate Lewis acid catalyst for the inverse electron demand Diels-Alder (IEDDA) reaction. The catalyst consists of a dihydroboranthrene core structure and its synthesis has been optimized to a convenient three step procedure. The new catalytic method was applied for the synthesis of a variety of different aromatic compounds, especially substituted naphthalenes. In addition, by the application of furans, domino processes have been discovered, were consecutively to the initial IEDDA reaction, depending on the furan substrate, either a [3,9] or a [1,9]-sigmatropic rearrangement occurred. In the case of the [3,9]-sigmatropic rearrangement the method was elaborated to produce substituted cyclopropanaphthalenes in excellent yields. Due to the unavailability of a general method for the synthesis of benzo-substituted phthalazines the range of applied 1,2-diazines was at first considerably reduced. This gap was filled with the development of a one-pot synthesis of substituted phthalazines and pyridazino-aromatics starting from commercially available aromatic aldehydes. Together with the catalytic IEDDA reaction the one-pot synthesis of 1,2-diazines comprised a novel two-step procedure to synthesize complex substituted naphthalenes and derivatives thereof. In order to put this powerful two step strategy into context, (±)-Naproxen, one of the most common non-steroidal anti-inflammatory drugs, was synthesized to demonstrate the utility of the methodology. The development of the catalytic methods as well as the mechanistic investigations were supported and corroborated by computational studies.