Stereocontrolled Synthesis of Substituted Chiral Piperidines viaOne-Pot Asymmetric 6π-Azaelectrocyclization: Asymmetric Syntheses of(−)-Dendroprimine, (+)-7-Epidendroprimine, (+)-5-Epidendroprimine, and (+)-5,7-Epidendroprimine

Abstract

The asymmetric one-pot 6π-azaelectrocyclization of alkenyl vinyl stannane, ethyl (Z)-2-iodo-4-oxobutenoate, and (-)-7-isopropyl-cis-aminoindanol in the presence of a Pd(0) catalyst stereoselectively produced the tetracyclic aminoacetal compounds, resulting from the four-bond formation accompanying by controlling the stereochemistry at the two asymmetric centers. The produced cyclic aminoacetals can be regarded as synthetic precursors of substituted chiral piperidines, and the syntheses of 2,4- and 2,4,6-substituted piperidines were realized from the obtained aminoacetals by the stereoselective hydrogenation of the double bond conjugated with the C-4 ester group and alkylation at the aminoacetal moiety. In addition, the stereoselective synthesis of an indolizidine alkaloid, (-)-dendroprimine, and its three stereoisomers, (+)-7-epidendroprimine, (+)-5-epidendroprimine, and (+)-5,7-epidendroprimine, were achieved.

Desymmetrization of Prochiral Cyclobutanones via Nitrogen Insertion: A Concise Route to Chiral γ‐Lactams

“…Based on Fujiokass tudies concerning halonium-initiated rearrangements of cyclobutanone aminals and ketals, [15] we started exploring chiral aminoalcohols that can be activated in situ by an appropriate halogen source.T hus,w ei dentified aminoindanol 2 and trichloroisocyanuric acid (TCICA) as af ormidable combination to convert prochiral 3-phenylcyclobutanone 1a to the corresponding g-lactam 3a (Table 1). [16] Under the optimized conditions (see SI for further information), high yield was achieved on small as well as gram-scale (Table 1, entries 1a nd 2). Considering the distance of the stereocenters,t he diastereomeric ratio (dr) of 80:20 was quite pleasing, especially since both isomers were easily separable by column chromatography.C hanging the solvent as well as decreasing the temperature led to incomplete conversions and/or the formation of side-products (Table 1, entries [3][4][5][6].…”

Desymmetrisierung von prochiralen Cyclobutanonen via Stickstoffinsertion: Ein einfacher Zugang zu chiralen γ‐Lactamen

“…So identifizierten wir Aminoindanol 2 und Tr ichlorisocyanursäure (TCICA) als eine hervorragende Kombination zur Umwandlung von Cyclobutanon 1a in das entsprechende g-Lactam 3a (Tabelle 1). [16] Unter optimierten Bedingungen (siehe SI fürw eitere Informationen) wurde eine hohe Ausbeute sowohl im Kleinals auch im Gramm-Maßstab erzielt (Tabelle 1, Nr.1und 2).…”

Asymmetric Synthesis of Natural Products and Medicinal Drugs through One-Pot-Reaction Strategies

“…For example, 292 was transformed into (-)-hippodamine after a series of reactions. Similar strategies were applied in the stereocontrolled synthesis of (-)-dendroprimine, (+)-7-epidendroprimine, (+)-5-epidendroprimine, (+)-5,7-epidendroprimine, 65 (-)-20-epiuleinevia, 66 and (-)-dendroprimine. 67 Scheme 52…”