Photoredox-Catalyzed Tandem Radical Cyclization/Hydroxylation for the Synthesis of 4-Hydroxyalkyl-3,3-difluoro-γ-lactams

Abstract

The photoredox-catalyzed radical difluoroalkylation/cyclization/hydroxylation cascade reaction of various 2-bromo-2,2-difluoro-N-arylacetamides containing unactivated alkene moieties has been developed, providing green and efficient access to various 4-hydroxyalkyl-3,3-difluoro-γ-lactams. Control experiments confirmed a radical process, and inexpensive air acted as the sole hydroxy resource. In addition, the highlights of this protocol include good tolerance for a variety functional groups, lower photocatalyst loading, and ease of operation.

Visible‐Light‐Driven Sulfonamidation of Arylazo Sulfonesthrough One‐Pot Multicomponent Reaction

“…Based on the control experiments and the previously published literatures, [40][41][42][43][44][45] a plausible mechanism for this visible-light-induced multicomponent transformation is pro-…”

“…Based on the control experiments and the previously published literatures, [40–45] a plausible mechanism for this visible‐light‐induced multicomponent transformation is provided (Scheme 4). With irradiation of blue LED light, aryl radical II is generated via activation of arylazo sulfone 1 a , followed by homolytic scission of the N−S linkage (1nπ* excited state).…”

“…[30][31][32][33][34][35][36][37][38] However, photochemical reactions often require expensive photocatalysts such as complexes of Ir or Ru metals or dye compounds. [39][40][41][42] Therefore, it is useful to develop novel photocatalyst-free photochemical reactions.…”

“…Typically, photochemical methods are effectively used for reactions involving radical pathways to form C−C coupling or carbon‐heteroatom bonds [30–38] . However, photochemical reactions often require expensive photocatalysts such as complexes of Ir or Ru metals or dye compounds [39–42] . Therefore, it is useful to develop novel photocatalyst‐free photochemical reactions.…”

Photoredox-Catalyzed Redox-Neutral Decarboxylative C–H Acylations of Coumarins with α-Keto Acid

“…Compared with other acyl sources, α-keto acids have become a better choice for the synthesis of related ketone derivatives because of their low cost, stability, easy preparation, and high reactivity. − The greener characteristic of the coproduct formed in reactions using α-keto acid (only CO 2 ), together with its versatility as a building block in catalytic organic synthesis, makes it a candidate for being a green acylating agent and an alternative to acyl chloride or other acyl transfer reagents. Photoredox catalysis has been regarded as an eco-friendly and effective strategy due to its convenience, availability, and safety. − Upon irradiation with visible light, conversion of α-keto acids into acyl radicals can be achieved via a single-electron transfer (SET) process by photocatalytic oxidation and subsequent decarboxylation. − However, in most cases, an additional oxidant or additive was essential. From the perspective of green chemistry, the development of the C–H acylation reaction under oxidant and additive free conditions is highly desirable.…”