Deacylative Alkylation vs. Photoredox Catalysis in the Synthesis of 3,3'‐Bioxindoles

Abstract

The synthesis of 3,3′-bioxindoles employing deacylative alkylations (DaA) in one-pot process, where the 3-bromooxindoles are generated in situ, is described. Good yields and moderate diastereoselections are obtained. By the modification of this procedure the synthesis of pure 3-bromooxindoles through a deacylative bromination (DaB) is achieved. These [a] C. 3101bromides are efficiently employed in a photoredox dimerization process to get the desired 3,3′-bioxindoles in good yields and low diastereoselections. In this single-electron-transfer (SET) mechanism the presence of a high quantum-yield iridium(III) complex ensures high conversions in short reaction times.The last strategy consists in an intramolecular dehydrogenative coupling (IDC) from the corresponding functionalized N-acyl-Scheme 1. General strategies employed for the synthesis of 3,3′-bioxindoles.

Dirhodium/Xantphos-Catalyzed Tandem C—H Functionalization/Allylic Alkylation: Direct Access to 3-Acyl-3-allyl Oxindole Derivatives from N-Aryl-α-diazo-β-keto Amides

“…Entries 8～11). Next, the reaction temperature was also investigated, and raising or lowering temperature slightly decreased the yield of the product 4a to 83% or 84%, respectively (Entries 12,13). Remarkedly, the control experiments demonstrated the essential role of Rh 2 (Oct) 4 and Xantphos in this catalytic system (Entries 14,15).…”

“…As described in Scheme 2, a rapid deacylative bromination of 4a was realized to afford the product 5 in 88% yield. [13] Furthermore, treatment of 4a with allylmagnesium bromide which upon workup generated the deacylated oxindole 6 (70% yield), then allyl Grignard addition to the C(2) carbonyl group of 6 was achieved to provide the medicinally important 2,3-disubstituted indole 7 in 75% yield. [14] Finally, the ring-closing metathesis of 7 with Grubbs-II catalyst delivered the synthetically challenging dihydrocarbazole derivative 8 in 76% yield.…”

n-selective Tsuji–Trost allylation promoted by a recyclable TSIL-palladium complex

“…Initially, allyl alcohol 5d was tested using 2-acetyltetralone (3l) employing both Methods A and B but the conversions observed in the crude 1 H NMR spectra were very low (not given in Table 2). However, employing the methodology developed by our group [36][37][38][39] dealing with the deacylative allylation (DAA) [40] employing 3-acetyl-3methyloxindoles 3o-q, the reaction was successful. Under aqueous conditions (Method B), the partial hydrolysis of oxindole 3o occurred although a notable conversion existed (not given in Table 2).…”

Photocatalytic Homocoupling Transformations

“…The homocoupling of these tertiary halides was induced by photocatalysis via novel stable-radical A. 57,58 The results (yields and diastereoselectivities) were similar in both methods from the corresponding halide (Scheme 25). However, bromides 79 were more accessible than the chlorides 77 employing a new deacylative bromination sequence (DaB).…”