Domino Elimination/Nucleophilic Addition in the Synthesis of Chiral Pyrrolidines

Polyhydroxylated pyrrolidines have been synthesized in a one-pot procedure by the addition of an organometallic reagent to isoxazolidines obtained by a 1,3-dipolar cycloaddition between nitrones and vinylsulfones. This method highlights sulfone reactivity and provides an easy approach for the preparation of chiral pyrrolidines using cyclic imines as key intermediates

Diastereoselective synthesis of chiral 1,3-cyclohexadienals

<div><p>A novel approach to the production of chiral 1,3-cyclohexadienals has been developed. The organocatalysed asymmetric reaction of different β-disubstituted-α,β-unsaturated aldehydes with a chiral α,β-unsaturated aldehyde in the presence of a Jørgensen-Hayashi organocatalyst provides easy and stereocontrolled access to the cyclohexadienal backbone. This method allows for the synthesis of potential photoprotective chiral 1,3-cyclohexadienals and extra extended conjugation compounds in a simple manner.</p></div

Synthesis of different chiral cyclohexadienals aromatic and non-aromatic compounds.

<p>Synthesis of different chiral cyclohexadienals aromatic and non-aromatic compounds.</p

General reaction to obtain chiral cyclohexadienals.

<p>General reaction to obtain chiral cyclohexadienals.</p

Experimental optimization of synthesis of chiral cyclohexadienals (4a, 4b) from citral (1) and α,β-unsaturated aldehyde 2.

<p>Experimental optimization of synthesis of chiral cyclohexadienals (4a, 4b) from citral (1) and α,β-unsaturated aldehyde 2.</p

The area of regions UVA (315–400 nm) and UVB (280–315 nm) and molar extinction coefficient of some cyclohexadienals (4a, 20b, 21b, 22b, 23a, 23b) dissolved in <i>i</i>PrOH.

<p>The area of regions UVA (315–400 nm) and UVB (280–315 nm) and molar extinction coefficient of some cyclohexadienals (4a, 20b, 21b, 22b, 23a, 23b) dissolved in <i>i</i>PrOH.</p

Synthesis of bicycle 12 from cyclohexadienal 4a.

<p>Reagents: a) NaH₂PO₄^.H₂O (2.2 equiv.), NaClO₂ (5%, 2.2 equiv.), 2-methyl-2-butene, <i>t</i>BuOH, r.t., 2h, 99%; b) <i>p</i>-TsOH, MeOH, r.t., 30%.</p

Proposal for the synthesis of new cyclohexadienal building blocks using different catalysts.

<p>Proposal for the synthesis of new cyclohexadienal building blocks using different catalysts.</p

Synthesis of chiral cyclohexadienals (20a-26) from other β-disubstituted-α,β-unsaturated aldehydes (13–19)^a.

<p>Synthesis of chiral cyclohexadienals (20a-26) from other β-disubstituted-α,β-unsaturated aldehydes (13–19)<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192113#t002fn001" target="_blank">^a</a>.</p

FDA approved UV-filters and bemotrizinol, approved only in Europe.

<p>The main UV filters structurally related to cinnamate esters, benzophenone, <i>p</i>-aminobenzoic acid (PABA) and salicilate derivatives, and two additional structures that can be found in ensulizole and bemotrizinol.</p