Dirhodium Carboxylate Catalysts from 2‐Fenchyloxy or 2‐Menthyloxy Arylacetic Acids: Enantioselective C−H Insertion, Aromatic Addition and Oxonium Ylide Formation/Rearrangement

Abstract

A new class of dirhodium carboxylate catalysts have been designed and synthesized from 2‐fenchyloxy or 2‐menthyloxy arylacetic acids which display excellent enantioselectivity across a range of transformations of α‐diazocarbonyl compounds. The catalysts were successfully applied to enantioselective C−H insertion reactions of aryldiazoacetates and α‐diazo‐β‐oxosulfones affording the respective products in up to 93 % ee with excellent trans diastereoselectivity in most cases. Furthermore, efficient desymmetrization in an intramolecular C−H insertion was achieved. In addition, these catalysts prove highly enantioselective for intramolecular aromatic addition with up to 88 % ee, and oxonium ylide formation and rearrangement with up to 74 % ee.

Flow photolysis of aryldiazoacetates leading to dihydrobenzofurans via intramolecular C–H insertion

“…60 With the optimised conditions established, the substrate scope was extended to include benzyl aryldiazoacetate 4 and isopropyl aryldiazoacetate 5. 53 In the absence of any photosensitiser with 10 minutes of photolysis, as seen in the transformation of 3 to 6a and 6b, an equimolar mixture of the cis and trans dihydrobenzofurans 7a : 7b and 8a : 8b was observed, with the trans and cis diastereomers being isolated in comparable yields after column chromatography (Table 4, entries 1-3).…”

“…Enantioselective rhodium carboxylate catalysed C–H insertions of aryldiazoacetate 3 to form dihydrobenzofurans leading to selective formation of the cis diastereomer, have been investigated by Hashimoto 54 and Davies, 55 with excellent enantioselectivity through appropriate choice of the rhodium catalyst. Having recently demonstrated that we can provide access to either dihydrobenzofuran 6a or 6b as a major product depending on the catalyst employed, with good enantiocontrol (Scheme 2), 53 we wished to explore if a similar transformation could be affected photochemically, providing the dihydrobenzofurans via a metal-free transformation.…”

“…Having recently demonstrated that we can provide access to † Electronic supplementary information (ESI) available. See DOI: https://doi.org/ either dihydrobenzofuran 6a or 6b as a major product depending on the catalyst employed, with good enantiocontrol (Scheme 2), 53 we wished to explore if a similar transformation could be affected photochemically, providing the dihydrobenzofurans via a metal-free transformation.…”

Development of novel transition metal-catalyzed synthetic approaches for the synthesis of a dihydrobenzofuran nucleus: a review

“…Buckley 60 et al in 2021 reported the synthesis of novel diastereoselective dirhodium carboxylate catalysts and employed them in the construction of 2,3-dihydrobenzofuran skeletons 72 , 73 . In their novel methodology, the stereoselective C–H insertion reaction of aryldiazoacetates 71 took place in the presence of catalytic amount of dirhodium catalyst 74 to furnish 2,3-dihydrobenzofuran units 72 & 73 with excellent trans enantiopurity (84% ee) and trans diastereoselectivity (>91 : 9 dr) in toluene (Scheme 10).…”

Research Progress on Enantioselective Desymmetrization Reactions Involving Metal Carbenes

“…2021 年, Maguire 课题组 [11] 发展了一类新颖的手性 双铑催化剂并成功应用于不对称的 Buchner 反应. 当使 用 α-重氮-β-氧代腈化合物 27 作为底物时, 该反应能以 90%的产率和 73%的 ee 值通过去对称化策略合成氮杂 薁酮类化合物 28 (Scheme 12).…”