Asymmetric tandem reactions: New synthetic strategies

Abstract

The use of domino and multicomponent reactions in asymmetric synthesis is constantly increasing nowadays. This allows for the synthesis of complex molecules in a single synthetic sequence, usually with high atom economy. Herein, we report three examples of new asymmetric tandem reactions recently developed in our laboratories, giving rise to new families of enantiomerically enriched fluorinated and nonfluorinated heterocycles. Thus, 1,4-dihydropyridines (1,4-DHPs) bearing fluorinated substituents at C6 were assembled by means of a Hantzsch-type reaction; cyclic β-amino carbonyl derivatives were prepared using a cross-metathesis (CM)-intramolecular aza-Michael sequence; while fluorinated indolines were obtained, for the first time, in a tandem nucleophilic addition-intramolecular aromatic substitution.

Tandem RCM–Claisen Rearrangement–[2+2] Cycloaddition of O,O'-(But-2-en-1,4-diyl)-bridged Binaphthols

“…A further requirement is that all reactions proceed under the same conditions with no mutual interference of by-products. Since advantages over conventional multistep synthesis by avoiding work-up and purification of intermediates are obvious, such processes have found widespread application [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. With increasing complexity of target structures functional group tolerance and stereoselectivity of transformations become crucial and are particularly challenging in the synthesis of natural products and biologically active compounds.…”

Tandem [4+2]/retro[3+2]/[3+2] cycloaddition reactions of fluorinated‐oxadiazoles with conjugated, unconjugated, cyclic, and acyclic dienes

“…[1][2][3][4] These objectives may be achieved efficiently by evoking tandem reaction processes in which multiple reactions take place sequentially in one synthetic operation. [5][6][7][8][9][10][11][12] In tandem reactions, an initial reaction produces intermediate(s) that are further engaged via their strategically positioned functional groups with other molecules in the reaction mixture to obtain the target adduct. 9 In addition to their pragmatic value, tandem reactions offer a highly selective synthetic approach to multiple chemical transformations, all in one pot.…”

“…The central goal of modern synthetic chemistry is to provide quicker, less expensive, and environmentally friendly synthetic routes to simple and complex molecules 1–4 . These objectives may be achieved efficiently by evoking tandem reaction processes in which multiple reactions take place sequentially in one synthetic operation 5–12 . In tandem reactions, an initial reaction produces intermediate(s) that are further engaged via their strategically positioned functional groups with other molecules in the reaction mixture to obtain the target adduct 9 .…”

Trifluoroacetic Anhydride Promoted Tandem Conjugate Addition of Boronic Acids/Acetal Ring Opening

“…Among the different types of conjugate addition reactions, tandem processes are particularly attractive, as these methods permit the construction of several C–C bonds in a one-pot process and the simultaneous generation of various stereocenters without isolation of intermediates. We disclose herein a new stereoselective tandem reaction which consists of the conjugate addition of boronic acids followed by the intramolecular ring opening of acetals under metal-free conditions (trifluoroacetic anhydride-promotion).…”