Nickel/Photo-Cocatalyzed Asymmetric Acyl C–H Allylation of Aldehydes and Formamides

Abstract

Herein, we developed a highly enantioselective acyl C−H allylation of aldehydes and formamides, which proceeds under the cooperative catalysis of a chiral PHOX nickel complex and tetrabutylammonium decatungstate (TBADT). With readily available Morita−Baylis−Hillman adducts as the electrophilic allylating agent, the reported reaction allows for the synthesis of α-stereogenic β,γ-unsaturated 1,4-dicarbonyl compounds in a highly enantioselective manner. The preliminary mechanistic investigations point to an enantioconvergent reaction pathway, in which rapid kinetic resolution of the starting allyl acetates through oxidative addition to Ni(0) is followed by dynamic kinetic resolution of the resultant allyl Ni(II) complexes via the interaction with acyl radicals generated by TBADT-mediated homolytic acyl C−H bond cleavage.

Asymmetric imino-acylation of alkenes enabled by HAT-photo/nickel cocatalysis

“…Subsequently, we varied the reaction parameters to demonstrate their inuence on the outcome of the target transformation. Only 7% ee could be achieved in the case of the PHOX L2 as the ligand, which has been proven to be the best ligand in our previously reported Ni/TBADT-cocatalyzed asymmetric reactions 14,15 (entry 2). In the case of the PyBox L3, the a Unless otherwise specied, the reactions were performed on a 0.2 mmol scale of the oxime ester 2a using 3 equiv.…”

“…9–11 Recently, the scope of C–H functionalization reactions involving TBADT has been significantly expanded through the combination of transition-metal catalysis. 12 We focus our research on the asymmetric variants of these reactions 13 and accomplished enantioselective olefin acyl-carbamoylation 14 and acyl C–H allylation, 15 which are the only two precedents in asymmetric cooperative catalysis of transition metals and TBADT to the best of our knowledge. As a continuation of our ongoing interest in this research area, we herein envision an asymmetric imino-acylation reaction of oxime ester-tethered alkenes with aldehydes through merging nickel-mediated enantioselective aza-Heck cyclization and TBADT-promoted acyl C–H activation, to allow for the synthesis of diverse pyrrolines bearing an acyl-substituted stereogenic center in a highly enantioselective fashion (Scheme 1B).…”

Asymmetric [3+n]‐Cycloaddition Reactions of Donor‐Acceptor Cyclopropanes

“…With C 1 ‐symmetric imidazoline‐pyrroloimidazolone pyridine L7 as the tridentate ligand which acted as a bifunctional chiral ligand and Co(OTf) 2 as the Lewis acid, diverse chiral indolizidine and benzo‐fused indolizidine derivatives 21 were obtained in good yields (up to 98 % yield), excellent diastereoselectivities (>20 : 1 dr ), and excellent enantioselectivities (up to 98 % ee ) (Scheme 11). [35] …”

Direct acylcyanation of aryl alkenes by dual photoredox and copper catalysis

“…7 A series of methods for generating acyl radicals have been developed by visible light catalysis. 8 For example, acyl radicals can be obtained from aldehydes, 9 α-keto acids, 10 carboxylic acids, 11 anhydrides, 12 acyl chlorides, 13 and other acyl donors such as acyl thioesters, 14 acyl silanes 15 and acyl metalloids 16 by the photocatalytic hydrogen atom transfer (HAT) or single electron transfer (SET) process. Among them, acyl chlorides are not only cheap and easy to obtain, but also can provide acyl radicals directly without other additives, effectively avoiding the prefunctionalization steps and elaborate catalytic strategies, making them a good choice.…”