Three-component, one-pot diastereoselective synthesis of 4-amidotetrahydropyrans via the Prins–Ritter reaction sequence

Synthesis of antiproliferative 13α-d-homoestrones via Lewis acid-promoted one-pot Prins–Ritter reactions of d-secosteroidal δ-alkenyl-aldehydes

“…1 H NMR spectra were recorded in DMSO-d 6 , CDCl 3 or C 6 D 6 solution with a Bruker DRX-500 instrument at 500 MHz, with Me 4 Si as internal standard. 13 C NMR spectra were recorded with the same instrument at 125 MHz under the same conditions. Full-scan mass spectra of the compounds were acquired in the range 50 to 800 m/z with an Agilent 500MS ion trap mass spectrometer equipped with an electrospray ionization source.…”

“…Prins-Ritter reaction of carbonyl compounds, homoallylic alcohols and nitriles, with phosphomolybdic acid as a solid catalyst [13]. Lewis acid catalysts such as BF 3 .OEt 2 , B(C 6 F 5 ) 3 , Bi(OTf) 3 and CeCl 3 .7H 2 O/AcCl, etc.…”

“…Lewis acid catalysts such as BF 3 .OEt 2 , B(C 6 F 5 ) 3 , Bi(OTf) 3 and CeCl 3 .7H 2 O/AcCl, etc. are also often used [9][10][11][12][13][14][15]. The products of the intermolecular reactions are usually obtained in good yields with cis selectivity.…”

“…Found: C, 80.11; H, 7.65%.2.1.4. Synthesis of 16α-N-acetyl-3-benzyloxy-13α-D-homoestra-1,3,5(10)-trien-17aα-acetate(13) 9b (100 mg, 0.23 mmol) was dissolved in pyridine (1 ml), and Ac 2 O (1 ml) was added. The mixture was stirred at room temperature for 24 h, poured onto water (50 ml) and extracted with CH 2 Cl 2 (3x15 ml).…”

Ritter Reaction: Recent Catalytic Developments

“…[24] On treatment of the homoallylic alcohols 25 (Scheme 18) and the aldehydes 23 or 24 in acetonitrile in the presence of PMA (20 mol-%), the cis-4-aminotetrahydropyrans 26 were isolated in good yields (80-92 %) and with high diastereoselectivities. In this Ritter-type process, the carbocation intermediates, generated in situ af- ter the PMA-mediated Prins reaction between the aldehydes and the homoallylic alcohols, are trapped by MeCN.…”