Studies on The Application of The Paternò-Büchi Reaction to The Synthesis of Novel Fluorinated Scaffolds.

In the context of new scaffolds obtained by photochemical reactions, Paternò-Büchi reactions between heteroaromatic, trifluoromethylphenyl ketone and electron rich alkenes to give oxetanes are described. A comprehensive study has then been carried out on the reaction of aromatic ketones with fluorinated alkenes. Depending on the substitution pattern at the oxetane ring, a metathesis reaction is described as a minor side process to give mono fluorinated alkenes. Overall, this last reaction corresponds to a photo-Wittig reaction and yield amid isosteres. In order to explain the uncommon regioselectivity of the Paternò-Büchi reaction with these alkenes, electrostatic-potential derived charges (ESP) have been determined. In a second computational study, the relative stabilities of the typical 1,4-diradical intermediates of the Paternò-Büchi reaction have been determined. The results well explain the regioselectivity. Further transformations of the oxetanes or previous functionalization of the fluoroalkenes open perspectives for oxetanes as core structures for biologically active compounds.

Tetrahydroquinolinyl phosphinamidates and phosphonamidates enhancing tolerance towards drought stress in crops via interaction with ABA receptor proteins.

New phosphorous-containing lead structures against drought stress in crops interacting with RCAR/(PYR/PYL) receptor proteins were identified starting from in-depth SAR studies of related sulfonamide lead structures and protein docking studies. A converging 6-step synthesis via phosphinic chlorides and phosphono chloridates as key intermediates afforded envisaged tetrahydroquinolinyl phosphinamidates and phosphonamidates. Whilst tetrahydroquinolinyl phosphonamidates 13a,b exhibited low to moderate target affinities, the corresponding tetrahydroquinolinyl phosphinamidates 12a,b revealed confirmed strong affinities for RCAR/ (PYR/PYL) receptor proteins in Arabidopsis thaliana on the same level as essential plant hormone abscisic acid (ABA) combined with promising efficacy against drought stress in vivo (broad-acre crops wheat and canola).

A modular sydnone cycloaddition/Suzuki-Miyaura cross-coupling strategy to unsymmetrical 3,5-bis(hetero)aromatic pyrazoles.

The [3 + 2] dipolar cycloaddition of 4-halosydnones with 1-haloalkynes opens a straightforward access to 3,5-dihalopyrazoles, valuable scaffolds for the elaboration of unsymmetrically 3,5-substituted pyrazole derivatives via site-selective Pd-catalyzed cross-coupling reactions. For instance, the flexible introduction of different (hetero)aryl substituents at the C-5 and C-3 positions of the PMP-protected pyrazole nucleus was achieved in a one-pot operation via sequential reactions with various boronic acids.