Visible‐Light‐Promoted Ring‐Opening Alkynylation, Alkenylation, and Allylation of Cyclic Hemiacetals through β‐Scission of Alkoxy Radicals

Abstract

The alkoxy radicals that are derived from cyclic hemiacetals have been generated through the visible‐light‐promoted reaction of the corresponding N‐alkoxyphthalimides with Hantzsch ester as the reductant. The alkoxy radicals subsequently undergo β‐scission of the C−C bond to generate carbon‐centered radicals, which are trapped by alkynyl‐, alkenyl‐, or allylsulfones.

Potential Degradation of 4‐Methyltetrahydropyran (4‐MeTHP) under Oxidation Conditions

“…OH, yields 4‐hydroxy‐3‐methylbutyl formate ( 8 ) [23] . Similar fragmentation reactions from the hemiacetal radicals corresponding to x under photolytic conditions have been previously reported [24–26] . Other oxidation products ( 3 , 4 and 5 ) are probably formed by mechanisms similar to those described in the m ‐CPBA oxidation.…”

Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp3)-H Bond Allylation

“…Our investigation was initiated by the serendipitous discovery with N-alkoxylphthalimide 1 as the alkoxyl radical precursor, which can be readily prepared from alcohols and are bench-stable (Scheme 2) (Zhu et al., 2009, Kim et al., 1998, Zhang et al., 2016, Zhang et al., 2017, Wang et al., 2016, Ito et al., 2018, Han et al., 2019, Deng et al., 2019, Shi et al., 2019). Under the reaction conditions of fac -Ir(ppy) 3 and Hantzsch ester known to generate alkoxyl radicals (Zhang et al., 2016, Zhang et al., 2017, Wang et al., 2016, Ito et al., 2018, Han et al., 2019, Deng et al., 2019, Shi et al., 2019), the ester-derived N-alkoxylphthalimide 1 gave no δ-C(sp 3 )-H allylation adduct 3 with allyl sulfone 2 under blue LED irradiation. Instead, the α-C(sp 3 )-H allylation adduct 4 was observed in 41% yield, together with the hydrogenation adduct alcohol 5 in 52% yield (entry 1 in Table 1) (Zhang et al., 2016).…”

Biomimetic Aerobic Epoxidation of Alkenes Catalyzed by Cobalt Porphyrin under Ambient Conditions in the Presence of Sunflower Seeds Oil as a Co-Substrate

“…Hence, LAOOH would readily be decomposed by CoPor into LAO· through O–O bond homolytic cleavage. , With respect to the strongest relative abundance of LAOH in the presence of CoPor (Figure B), LAOOH probably converted into LAOH via LAO· through H-abstraction. In addition, LAO· would likely to be converted into the corresponding fatty aldehyde through homolytic β-scission. − …”