Overcoming the Deallylation Problem: Palladium(II)-Catalyzed Chemo-, Regio-, and Stereoselective Allylic Oxidation of Aryl Allyl Ether, Amine, and Amino Acids

Abstract

We report herein a Pd(II)/bis-sulfoxide-catalyzed intramolecular allylic C−H acetoxylation of aryl allyl ether, amine, and amino acids with the retention of a labile allyl moiety. Mechanistically, the reaction proceeds through a distinct double-bond isomerization from the allylic to the vinylic position followed by intramolecular carboxypalladation and the β-hydride elimination pathway. For the first time, C−H oxidation of N-allyl-protected amino acids to furnish five-membered heterocycles through 1,3-syn-addition is established with excellent diastereoselectivity.

Recent progress in catalytic acyloxylation of C(sp3)‐H bonds

“…[ 78 ] Therein, formation of deallylation products was suppressed via addition of bis ‐sulfoxide ligand, affording products of the type 112 and 114 with six‐ or five‐membered rings with high chemo‐, regio‐ and stereoselecitivity (Scheme 17). [ 77 ]…”

“…More recently, Jana with coworkers reported an interesting example of Pd(II)-catalyzed intramolecular allylic C(sp 3 )-H acetoxylation of aryl allyl ethers, amines and amino acids of the type 111 and 113 using Pd(OAc) 2 as catalyst and BQ as oxidant. [77] Allylic functionalizations with retention of the heteroatom (O, N) attached allyl moiety have been extremely rare because of the undesired deallylation under palladium catalysis. [78] Therein, formation of deallylation products was suppressed via addition of bis-sulfoxide ligand, affording products of the type 112 and 114 with six-or five-membered rings with high chemo-, regio-and stereoselecitivity (Scheme 17).…”

“…[78] Therein, formation of deallylation products was suppressed via addition of bis-sulfoxide ligand, affording products of the type 112 and 114 with six-or five-membered rings with high chemo-, regio-and stereoselecitivity (Scheme 17). [77] 2.1.7 | Acyloxylation of other substrates Aromatic ketones and aldehydes have been rarely used as substrates for the C(sp 3 )-H acyloxylation reactions, because of the propensity of the CHO group to undesired oxidation, as well as competitive metal insertions into formyl C-H bonds and the weak coordination ability of carbonyl groups. Nevertheless, over the last few years several successful examples of such transformations were reported.…”

Protocol for chemo- and regioselective C(sp3)–H activation using a heterogeneous copper powder-catalyzed reaction

“…Thus, for the non-directed C(sp 3 )−H bond activation, choosing weaker C(sp 3 )−H bonds (e.g., benzyl, allyl etc.) over unbiased strong alkyl C(sp 3 )−H bonds have been more fruitful ( Feng et al., 2012 ; Golden et al., 2022 ; Liu et al., 2013 , 2020 ; Lu et al., 2017 ; Manna et al., 2020 ; Nandi and Jana, 2022 ; Rout et al., 2014 ; Suh et al., 2020 ; Vasilopoulos et al., 2017 ).…”

DMSO–allyl bromide: a mild and efficient reagent for atom economic one-pot N-allylation and bromination of 2°-aryl amines, 2-aryl aminoamides, indoles and 7-aza indoles

“…To substantiate the formation of deallylation products (10a′–b′) formed during competitive Heck coupling, 33 a model reaction was performed with allylated compound 5a under similar reaction conditions, deallylation product 1a was observed ( Scheme 5 ).…”