Synthetic and Computational Study of the Enantioselective [3+2]-Cycloaddition of Chromones with MBH Carbonates

Abstract

Highly efficient and straightforward access to enantioenriched five-membered ring-fused chromanones is developed via [3+2]-cycloaddition of 3-cyanochromones with Morita− Baylis−Hillman carbonates. Densely functionalized chiral cyclopenta[b]chromanones with three continuous quaternary and tertiary stereogenic carbon centers were obtained in high yields with high ee and dr (≤97% yield, 97% ee, and >20:1 dr). Moreover, density functional theory calculations have been carried out to investigate the mechanism and regio-and diastereoselectivity of the reaction.

A Synthesis of α-Alkyl Cycloenones by Pd-Catalyzed Suzuki–Miyaura Coupling with Cyclic Morita–Baylis–Hillman Adducts

“…1b and 1c were prepared by the same method as 1a . 1d and 1e were prepared according to the literature report.…”

tert-Butyl Nitrite-Induced Radical Nitrile Oxidation Cycloaddition: Synthesis of Isoxazole/Isoxazoline-Fused Benzo 6/7/8-membered Oxacyclic Ketones

“…: 135-136 • C. 1 H NMR (500 MHz, CDCl 3 ) δ (ppm) 7.90 (d, J = 8.0 Hz, 1H), 7.05 (dd, J = 8.0, 1.6 Hz, 1H), 6.92 (d, J = 1.6 Hz, 1H), 4.83 (dt, J = 10.3, 4.4 Hz, 1H), 4.27 (ddd, J = 7.1, 5.8, 4.0 Hz, 1H), 3.69 (dd, J = 10.4, 7.1 Hz, 1H), 2.38 (s, 3H), 2.14 (dddd, J = 37.4, 13.8, 10.9, 5.7 Hz, 2H), 1.95-1.75 (m, 3H), 1.74-1.53 (m, 2H). 13 C NMR (126 MHz, CDCl 3 ) δ (ppm) 184.5, 161.1, 158.5, 147.9, 129.8, 126.9, 125.9, 123.6, 80.9, 77.8, 49.6, 27.9, 23.9, 21.7, 14.7. HRMS (ESI): m/z [M + H] + calcd for C 15 H 16 NO 3 : 258.1125; found: 258.1123.…”

“…Column chromatography was performed by using silica gel (200-300 mesh). The 1 H NMR and 13 C NMR spectra were recorded on a Bruker Advance 500 MHz instrument at 500 MHz ( 1 H NMR) and 126 MHz ( 13 C NMR). We used the residual solvent peak in CDCl 3 as an internal reference (δ = 7.26 for 1 H and δ = 77.0 for 13 C{ 1 H}).…”

Metal-free synthesis of difluoro/trifluoromethyl carbinol-containing chromones via tandem cyclization of o-hydroxyaryl enaminones

“…[19][20][21][22] Thus, effective methods for the synthesis of various functional chromones and their derivatives have received extensive attention, particularly for fluorine-containing chromones. [23][24][25][26][27][28][29][30] In 2020, Liu and co-workers reported a free-radical-initiated cross-dehydrogenative-coupling of trifluoroethanol with chromones for the synthesis of C2 trifluoromethyl chromones (Scheme 1a). 31 The tandem reaction involving chromone cyclization of o-hydroxyphenyl enaminones is a commonly used strategy for the synthesis of 3-substituted chromones.…”