Suzuki−Miyaura Cross-Coupling of Potassium Trifluoroboratohomoenolates

Abstract

Ketone-, ester-, and amide-containing potassium trifluoroboratohomoenolates were prepared in good to excellent yields from the corresponding unsaturated carbonyl compounds. They were shown to be effective coupling partners in the Suzuki-Miyaura reaction with a variety of electrophiles including electron-rich and electron-poor aryl bromides and -chlorides.

Tandem β‐Boration/Arylation of α,β‐Unsaturated Carbonyl Compounds by Using a Single Palladium Complex To Catalyse Both Steps

“…The substrate (E)-isobutyl but-2-enoate, with a bulkier ester moiety, was also efficiently b-borated with catalytic system 3, but less so with 4, 7, and 8 (Table 3, entries 9-13), even after longer reaction times. A similar trend was observed when a-substituted a,b-unsaturated esters were used in the reaction, in that while (E)-methyl 2-methylbut-2-enoate was conveniently transformed into the b-organoborated product with catalytic system 3 ( Table 3, entry 14), the analogous substrates (E)-ethyl 2-methylbut-2-enoate and (Z)-isobutyl 2-methylbut-2-enoate were only b-borated with low or moderate conversions, even after reaction times of 16 or 24 h (Table 3, entries [15][16][17][18][19]. Therefore, the nature of the ester moiety seems to play an important role in the b-boration reaction as far as the substrate is concerned, and catalytic system 3 seems to be the most efficient, probably because it contains only two P,N ligands.…”

“…THF was the solvent of choice for the two consecutive reactions, because the use of toluene reduced the efficiency of the cross-coupling transformation. The amide homoenolate cross-coupling reaction has only been reported by Molander et al, [16] and their yields were moderate even when the potassium trifluoroboratohomo-A C H T U N G T R E N N U N G enolate analogue was used. While they required two different catalytic systems (Cu I /DPEPhos/NaOtBu and Pd II / RuPhos/K 2 CO 3 ; DPEPhos = bis(2-diphenylphosphinophenyl) ether, RuPhos = (3-diethoxyphosphinothioylsulfanyl-1,4-dioxan-2-yl)sulfanyldiethoxysulfanylidenephosphorane) to perform the three steps (Scheme 10), we only needed the dinuclear palladium complex as a single catalytic system in a one-pot protocol.…”

“…It was revealed that amides reacted with B 2 pin 2 much more rapidly than the corresponding esters. Similarly, Molander et al [16] reported the preparation of trifluoroboratohomo-A C H T U N G T R E N N U N G enolates from tertiary a,b-unsaturated amides by employing Cu I salts and KHF 2 . The asymmetric version was conducted by Yun et al [20] using Cu I catalytic systems modified with chiral bidentate ligands.…”

Aryl/heteroaryl pentafluorobenzenesulfonates (ArOPFBs): new electrophilic coupling partners for room temperature Suzuki–Miyaura cross-coupling reactions

“…9 Accordingly, we used a deactivated 3,5-dimethoxyphenyl pentafluoro benzenesulfonate and 4-methoxyphenyl boronic acid as the model substrate for optimization of reaction conditions (Table 1). Also, a procedure employed by Buchwald et al for the carbon-carbon bond forming process of tosylates was used on our model substrate.…”

“…Evaluation of Pd sources using mild catalysts like Pd(PPh 3 ) 2 Cl 2 , Pd(PPh 3 ) 4 , PdCl 2 , Pd(OAc) 2 , Pd(CH 3 CN) 2 Cl 2 as shown in Table 1. However, the use of Pd(PPh 3 ) 2 Cl 2 provided the best results (Table 1, entry 6, [9][10][11]. Among the bases screened, use of K 3 PO 4 .H 2 O and KOAc were found to give superior results (Table 1).…”