ElectronTransfer Induced Ring Opening of α-Epoxyketones: Spirodioxolane Formation

Abstract

Stereospecific formation of spirodioxolanes has been observed on electron transfer induced ring opening of α-epoxyketones by 2,4,6-triphenylpyrylium tetrafluoroborate in the presence of cyclohexanone.

Photoinduced electron transfer ring opening of α-epoxyketones using 7,7,8,8-tetracyano-p-quinodimethane (TCNQ)

“…All photoproducts are known and their spectroscopic data have been already reported [14][15][16][17]. 1 H NMR spectra were measured in CDCl 3 solutions containing TMS as an internal standard on Bruker AW 80 (80 MHz) and Bruker DRX-500 (500 MHz) spectrometers.…”

“…The calculated values of the total dipole moment of the molecules show, again, the effect of the donor group on the polarity of the Table 4. Photocatalytic Ring Opening of 1a-1e and 1g in Cyclohexanone Solution by TPT [17] (2) and TCNQ (12 …”

“…E-mail: memarian@sci.ui.ac.ir in methanol [14], acetic acid [15], acetone [16], and cyclohexanone [17] solutions. As a continuation of our studies with -epoxyketones, we have investigated their electrondonor ability toward photoexcited TCNQ (12) in methanol, acetic acid, acetone, and cyclohexanone solutions to elucidate the effect of the electron acceptor (photocatalyst) on the rate of the ring opening and on the diastereoselectivity of the reaction.…”

Diastereoselective 1,3-Dioxolane Formation by Photocatalytic Ring Opening of α-Epoxyketones

“…Whereas irradiation of 1a -f in the presence of pyrylium salt 2 in dry acetone resulted in the formation of diastereomeric cis-and trans-1,3-dioxolanes 5a -f and 6a -f besides the formation of alcoholic by-products 7 and 8 [16], diastereospecific formation of cis-spirodioxolanes 9a -f is observed by carrying out the irradiation in cyclohexanone solution (Scheme 2) [15]. An interesting point is that the irradiation of 1a -f in the presence of TCNQ (3) in acetone resulted in the formation of cis-1,3-dioxolanes 5a -f besides the formation of alcoholic by-products 7 and 8 [19], while by using the photocatalyst 4, the formation of cis-1,3-dioxolanes 5a -f accompanied by the formation of a trace amount of trans-1, 3 6a -f is observed [20].…”

Photosonochemical catalytic ring opening of α-epoxyketones

“…Recently, we have reported on the photocatalytic ring opening of α-epoxyketones 1a-f and 2,4,6-triphenylpyrilium tetrafluoroborate (TPT) as photocatalyst in methanol, [37] cyclohexanone, [38] acetone [39] and acetic acid solutions. [40]…”