We propose the synthesis of biologically relevant hexahydro‐1H‐pyrano[3,4‐c]chromenes, via a tandem Prins/Friedels‐Crafts process, catalyzed by BF3.Et2O, starting from (E)‐ and (Z)‐5‐phenoxypent‐3‐en‐1‐ol. The diastereoselectivity of the process is controlled by the geometry of the homoallylic alcohol. We also point out that the Prins product can be obtained in high yields and good diastereoselectivity when the reaction is promoted by AlCl3 as Lewis acid in the presence of an external nucleophile.
A strategy has been developed for the synthesis of dispiro‐3H‐indoles by employing a 3‐({[2‐(1H‐indol‐3‐yl)ethyl]amino}methyl)but‐3‐en‐1‐ol derivative and various aldehydes in a sequential Prins/Friedel–Crafts cyclization in the presence of readily accessible trifluoroacetic acid (TFA) under mild conditions over a short period of time. This method proceeded smoothly with a wide range of aldehydes and provided the products in good yields with a broad pattern of substituents.
A substituent controlled aza‐ene/Prins cyclization strategy has been developed for the one‐pot synthesis of dihydroquinoline tethered tetrahydropyran derivatives from ortho‐aminoaryl alkenols and aromatic aldehydes using 30 mol% TMSOTf at 60 °C. The reaction proceeds through a sequential aza‐ene and Prins cyclization. In the case of nitro and cyano substituted aromatic aldehydes, eight‐membered oxocene derivatives were obtained under similar conditions. This is the first report on the introduction of tetrahydropyran ring at 4th position of dihydroquinoline from ortho‐aminoaryl alkenol and aromatic aldehyde in the presence of an acid catalyst. A catalytic amount of TMSOTf facilitates aza‐ene and Prins cyclizations sequentially in a single‐step.
Correction for ‘Tandem Prins cyclization for the synthesis of indole fused spiro-1,4-diazocane scaffolds’ by Chandrashekhar Rapelli et al., Org. Biomol. Chem., 2020, 18, 6710–6715, DOI: 10.1039/D0OB01384F.
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