TEMPO-Promoted Domino Heck–Suzuki Arylation: Diastereoselective Cis-Diarylation of Glycals and Pseudoglycals

Abstract

A palladium-catalyzed regio- and diastereoselective diarylation of glycals and pseudoglycals, which is a kind of Heck-Suzuki arylation, is described. A wide range of arylboronic acids reacted under these conditions smoothly. Selectivity was C1-C2(α,α) in the case of glycals but C2-C3(β,β) for pseudoglycals. Quantum chemical analysis has been carried out to establish the reaction mechanism, which may involve Pd(II)/Pd(O). TEMPO plays a key role in the formation of diaryl glycoside due to its radical nature.

Diastereoselective Synthesis of trans‐2,3‐Diaryl(heteroaryl)‐3,6‐dihydropyrans by an Allylboration/Ring‐Closing‐Metathesis Sequence

“…First, (3-phenylallyl)borane was prepared in situ by treatment of 1a with bis-(pinacol-borane) [(Bpin) 2 (2.2 equiv.)] in the presence of a palladium catalyst [Pd(CH 3 CN) 4 (BF 4 ) 2 ] in a mixture of DMSO/MeOH (1:1) at 50°C. After 2 h, the reaction mixture was worked up, and aryl(heteroaryl) aldehydes 2a-2f were treated with the crude pinacolboronates in CH 2 Cl 2 to produce the desired homoallylic alcohols 3a-3f in good yields (87-99 %).…”

“…[2] So far, arylation reactions of glycals and glycosides have been restricted to monoarylation. [4] These compounds can also be obtained by construction of the oxygen-containing sixmembered rings. [4] These compounds can also be obtained by construction of the oxygen-containing sixmembered rings.…”

Transition Metal‐Catalyzed Dicarbofunctionalization of Unactivated Olefins

“…The reaction was proposed to proceed via coordination‐assistance by the N,N ‐dimethylamino group tethered to vinyl ethers that would form a palladacycle ( 15 ) in situ to prevent β‐H elimination from a C(sp 3 )‐PdX intermediate. Recently, Mukherjee and coworkers also demonstrated an oxidative 1,2‐diarylation of olefins in glycals and pseudoglycals with ArB(OH) 2 using Pd(OAc) 2 as a catalyst where excess TEMPO functioned as a promoter of the reaction (Scheme ) …”

Homogeneous Catalysis: A Powerful Technology for the Modification of Important Biomolecules

“…Ap alladium-catalyzed diarylation of glycals 38 and pseudoglycals 35 with aryl boronic acids 36,w hich involved aH eck-Suzuki-type reaction, was described by Mukherjee and coworkers (Scheme 10). [40] This reactionw as highly regio-and diastereoselective,t herebyg iving the C1ÀC2 (a,a)-isomers of the diarylated products (39)w ith glycals 38 and the C2ÀC3 (b,b)-isomers (37)w ith pseudo-glycals 35.I nt his case, the addition of TEMPOw as essential for circumventing syn-/anti-elimination.…”