Construction of Chiral 2‐Substituted Octahydroindoles from Cyclic Ketones and Nitroolefins Bearing only One α‐Substituent

Abstract

A dual catalytic system has been developed following the screening of a series of chiral primary amine catalysts and chiral phosphoric acid catalysts for the Michael addition of cyclic ketones to nitroolefins bearing only one a-substituent. The resulting g-nitro ketones, which contain a substituent on the carbon connected to the nitro group, were formed in excellent yields (> 80%) with high levels of stereoselectivity (up to 94:6 dr and 98% ee) when the reaction was performed in benzene at 0 8C with 10 mol% of the optimal amine/phosphoric acid combination (1:1) as a catalyst. Subsequent reduction of the nitro group followed by intramolecular reductive amination could afford optically active cis-octahydroindole analogues bearing a non-functional substituent at their 2-position.

Synthesis of Triazolo[c]coumarins and Differences in the Fluorescence Properties of Their Isomers

“…Using reported coumarin precursors [2] and phenylethyl azide [16,17] as model substrates, we investigated appropriate conditions for the synthesis of coumarins. The coumarin precursors 1 , 2 and 3 were prepared based on previously reported synthetic schemes [2,18,19] .…”

On the Enantioselective Phosphoric-Acid-Catalyzed Hantzsch Synthesis of Polyhydroquinolines

“…In the literature, catalysts I and II scarcely allow the reaching of high enantiomeric excesses, and bulkier congeners such as III are often preferred …”

“…It appeared unclear how such diversified chemical entities that are likely to proceed by different modes of activation could result in very similar results. Moreover, all chiral catalysts but the phosphoric acids resulted in negligible enantioinduction. In the literature, catalysts I and II scarcely allow the reaching of high enantiomeric excesses, and bulkier congeners such as III are often preferred An enantiomeric excess determination for product 4b (98% ee) was performed by HPLC on chiral stationary phase using an Astec Chirobiotic V2 column (Figure a) .…”

Synthesis of a New Lopinavir Phosphinic Analog as HIV-1 Inhibitor

“…According to the retrosynthetic analysis study, four main fragments are present in PL1, a-d, which come from the disconnections 1 -3. As shown in Figure 2, fragment a corresponds to the Cbz-(R)-Phe-PO 2 H 2 [9], fragment b come from an acid chloride, fragment c corresponds to (2-nitroallyl) benzene [10], and fragment d to a valine analog [11].…”