Sequential Oxidation-Prins Reaction Processes Induced by the Same Iron Salt: Direct Access to 2-Aryl-4-Chloro-Tetrahydropyrans from Benzyl ­Alcohols

Abstract

A clay-supported iron(III) nitrate (Clayfen) was used as a stoichiometric reagent to first oxidize benzylic alcohols. The aldehydes thus obtained were converted in situ into tetrahydropyrans by way of a Prins cyclization induced by iron species already present in the media.

Preparation of trans-2-Substituted-4-halopiperidines and cis-2-Substituted-4-halotetrahydropyrans via AlCl3-Catalyzed Prins Reaction

“…cis -2-(4-Bromo­phenyl)-4-chloro­tetrahydro-2 H -pyran (major diastereomer, white solid, mp = 64–65 °C): 1 H NMR (400 MHz, CDCl 3 ) δ = 7.36 (d, J = 8.4 Hz, 2H), 7.09 (d, J = 8.3 Hz, 2H), 4.14 (d, J = 11.2 Hz, 1H), 4.08–3.93 (m, 2H), 3.43 (td, J = 12.2, 1.7 Hz, 1H), 2.24–2.17 (m, 1H), 2.02 (dd, J = 12.9, 2.1 Hz, 1H), 1.84 (qd, J = 12.4, 4.8 Hz, 1H), 1.72–1.67 (m, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ = 140.5, 131.6, 127.6, 121.6, 78.5, 67.3, 55.5, 44.6, 36.8. NMR data were in agreement with the reported results …”

“…IR: 3051,2901,1595,1486,1451,1347,1161,844,660 cis-4-Bromo-2-(2-fluorophenyl)-1-tosylpiperidine (minor diastereomer, oil): 1 H NMR (400 MHz, CDCl 3 ) δ = 7.43 (d, J = 8.0 Hz, 2H), 7.25 (t, J = 7.4 Hz, 1H), 7.14 (d, J = 7.8 Hz, 3H), 6.97 (t, J = 7.4 Hz, 1H), 6.86−6.79 (m, 1H), 4.67 (dd, J = 7.4, 5.0 Hz, 1H), 4.10− 3.99 (m, 1H), 4.00−3.87 (m, 1H), 3.30−3.07 (m, 1H), 2.57−2.42 (m, 1H), 2.33 (s, 3H), 2.30−2.21 (m, 1H), 2.15 (dd, J = 13.6, 3.8 Hz, 1H), 2.04 (dd, J = 11.4, 7.6 Hz, 1H). 13 C NMR (100 MHz, CDCl 3 ) δ = 159.0 (d,J = 245.2 Hz),143.5,129.5,129.2,129.1 (d,J = 3.8 Hz),127.4,123.9 (d,J = 3.4 Hz),115.4 (d,J = 22.3 Hz),54.1,45.0,43.9,40.4,34.9, 21.6. 19 F NMR (376 MHz, CDCl 3 ) δ = −116.4.…”

A new and facile CuCl2·2H2O-catalyzed one-pot three-component synthesis for quinazolines

“…One-pot protocols are fascinating as they dodge isolation of different compounds and are generally better yielding in comparison with stepwise reactions [24]. Design of quinazoline-based drugs has reincarnated the curiosity in developing new synthetic protocols for the syntheses of this valuable nucleus.…”