New Cyclohexadienone Derivatives: Preparation and Chiral Discrimination in High-Pressure Diels-Alder Cycloadditions

Abstract

A wide range of cyclohexadienones has been synthesised in order to study their reactivity and their regio- and stereoselectivity with the enantiopure diene 1 under high-pressure conditions. Computational investigations were used to point out some parameters which affect the reactivity in this high chiral discrimination process. In addition, the resulting [4+2] cycloadducts allowed the preparation of new polyfunctional cyclohexenone derivatives.

Asymmetric transformations of achiral 2,5-cyclohexadienones

“…In a later report, the Winterfeldt group described an in depth investigation of the Diels–Alder reaction. 53 This study also included a cycloaddition/reduction sequence ( 177→178 ) that, upon release of enone 179 , would correspond to a formal enantioselective hydrogenation of a cyclohexadienone; however, the authors did not perform the cycloreversion on this particular substrate.…”

High pressure chiral recognition experiments – a route to homochiral 4-fluorocyclohexenones

“…In order to demonstrate the rate enhancing effects of the fluoro atom 7 we started with a high pressure competition experiment employing methyl derivative 5a, which had already been shown to undergo high yielding, diastereoselective cycloadditions at 6,5 kbar, 5 and the corresponding quinol 8 (Scheme 3). Although this competition experiment was run at 14 kbar for six days, only the fluoro derivative 9a was formed and proved to be identical to the product obtained earlier at 6,5 kbar.…”

“…4,5,6,7 In the latter case, cycloadditions with cyclohexadienones of type 2 were shown to follow the very obvious pathway which places the small residue "S" into the α-endo-position (Scheme 1). …”

The Total Synthesis of (±)‐Fortucine and a Revision of the Structure of Kirkine

“…Furthermore, it was hoped that the cyclizations would be stereoselective, to furnish the requisite cis B/C-ring junction, and regioselective, to give the para (as opposed to ortho) cyclized product with respect to the benzyloxy group. The key precursor would be constructed by the union of p-benzoquinone ethylene monoketal (7) [7] with the azaenolate of hydrazone 8 [8] . It is worth noting the convergent manner by which rings A and C are appended upon hydrazone 8, which in turn provides the foundation of ring D.…”