Iodine-Catalyzed Oxidative Coupling To Construct C–O Bonds for the Synthesis of 2,3-Dihydrooxepines

Abstract

The iodine-catalyzed catalytic formal [3 + 3 + 1] cycloaddition for the preparation of a seven-membered O-heterocyclic ring is presented, which is an achievement of methyl and carbonyl group reactivity of 3-methyl-5-pyrazolones to forge the C-O bond. This novel protocol provides a straightforward and efficient access to structurally diverse fused O-heterocycles through an iodine-catalyzed iodination/Kornblum oxidation/oxidative coupling/C-O bond formation cascade reaction. This approach demonstrates the unprecedented concurrent realization of the unique reactivity among the methyl, methylene, and carbonyl groups in 3-methyl-5-pyrazolones for the construction of 2,3-dihydrooxepine rings. Moreover, a broad substrate scope displays a graceful diversity-oriented synthetic approach.

Iodine‐Promoted Domino Oxidative Cyclization for the One‐Pot Synthesis of Novel Fused Four‐Ring Quinoxaline Fluorophores by sp3 C−H Functionalization

“…Considering the results presented above and the previous reports,– a proposed mechanism is shown in Scheme . Initially, 1 a reacted with I 2 to afford intermediate 1 aa , which is subsequently converted to 2‐aldehyde indolium iodide 1 ab through a Kornblum oxidation in the presence of DMSO .…”

Iodine‐Catalyzed Construction of Dihydrooxepines via 3‐Methyl‐5‐Pyrazolones C−H Oxidation/Functionalization of Quinolines Cascade

“…Soon after, Mascareñas and Gulías’ group used a Rh‐catalyzed cycloaddition strategy involving a C−H activation process to realize an efficient construction of benzoxepines (Scheme 1b) [10] . In 2017, Wu's group developed I 2 ‐catalyzed with an organic strong acid to construct Dihydrooxepines (Scheme 1c) [11] . The use of precious metals and additive is necessary in the previous works, but reported herein is the use of iodine catalysis without additive to describe a successful design process involving the functionalization of quinolines and three‐component cyclization of 3‐methyl‐5‐pyrazolones.…”

An iodine-promoted one-pot and metal-free access to indolin-2-ones

“…19,20 An in situ iodination usually occurs in iodinemediated oxidative couplings, followed by in situ oxidation to generate an electrophilic aldehyde group. [21][22][23] 1,2,3,3-Tetramethyl-3H-indolium iodide, a well-known synthetic agent of many fluorescent dyes, is considered to contain an activated methyl group which can react with an aldehyde or carbonyl group. 24,25 In our previous research, the activated C-2 methyl group reacted with molecular iodine to form an aldehyde via Kornblum oxidation in the presence of dimethyl sulfoxide (DMSO).…”