Catalytic Enantioselective Arylation of Glyoxylate with Arylsilanes: Practical Synthesis of Optically Active Mandelic Acid Derivatives

Abstract

Just a little does the trick! The catalytic enantioselective arylation using chiral dicationic palladium complexes provides a reliable and useful access to enantiomerically enriched mandelic‐acid derivatives. Significantly low catalyst loading (down to 0.002 mol %) as well as easy catalyst handling are the advantage of this practical method.

Catalytic and highly enantioselective Friedel–Crafts type reactions of heteroaromatic compounds with trifluoropyruvate and glyoxylate by a dicationic palladium complex

“…dicationic Pd-catalyst 1a (5 mol%) prepared in situ from the corresponding dichloride complex and two equivalents of AgSbF 6 10 (Scheme 2). As shown in the literature, 9 the reactions with ethyl glyoxylate 3 proceeded regioselectively at the 2position even at -40 °C to give product 6a in excellent yield and enantioselectivity after the desilylation of siloxy product 6a' (Scheme 2,Eq. 2).…”

Enzymatic Enantioselective Decarboxylative Protonation of Heteroaryl Malonates

“…Enantioselective Friedel-Crafts reactions between aryl compounds and glyoxylates have been developed that utilise chiral Cu and Ti catalysts, [20,[28][29][30] and enantioselective arylation of glyoxylates using aryl silanes and chiral Pd catalysts have also been developed. [31] However, in both of these approaches the chiral catalysts are expensive and/or utilise toxic transition metal species. Also, some of the transition-metal catalysts used result in a-hydroxy acetic acids with only modest ee relative to our enzymatic method.…”

Chemical Constituents from the Stems of Excoecaria acertiflia

“…Compound 6 was derived from ethyl (R)-4,7-dihydroxy-3-methoxybenzeneacetate by the replacement of the OH groups at C(4) with a CH 2 OH group, which was verified by the HMBCs (Fig. The configuration at the only stereogenic center C(7) in compound 6 was determined as (R), based on the comparison of the [a] 21 D ¼ À 12.62 (c ¼ 1.50, MeOH) of 6 with [a] D ¼ À 88.3 (c ¼ 1.50, MeOH) of an analogous homolog [19]. Other HMBCs and 1 H, 1 H-COSY correlations (Fig.…”

“…(þ)-cyclolariciresinol [13], secoisolariciresinol [14], isolariciresinol-4'-ether [14], (7S,8S)-nitidanin [15], (7S,8S)-5-hydroxynitidanin [15], nocomtol [16], americanin A [17], integracin B [18], (R)-4,7-dihyroxy-3-methoxybenzeneacetic acid ethyl ester [19], (S)-4,7-dihydroxy-3-methoxybenzeneacetic acid ethyl ester [19], 1,2-bis(4-hydroxy-3methoxyphenyl)propane-1,3-diol [20], cinchonain Ib [21], ethyl (þ)-3-hydroxycyanidane-8-carboxylate [22], and linarigenin [23].…”

“…The 13 C-NMR and DEPT spectra ( Table 1) showed 20 C-atom resonances, including those of four Me, four CH 2 (one olefinic), five CH groups (one O-bearing and three olefinic), and seven C-atoms (one C¼O and two olefinic). 2) from HÀC(1) (d(H) 6.31 (s)) and Me (19) (d(H) 1.26 (s)) to C(3) (d(C) 200.6 (s)), and from Me(18) (d(H) 1.09 (s)) to C(1). Comparing their 13 C-NMR data, the major differences consisted in the position of the C-atom signals at d(C) 123.2 (d, C(1)) and 145.0 (s, C(2)) of 1 instead of the signals at d(C) 35.1 (t, C(1)) and 34.2 (t, C(2)) in excocarinol A, indicating that 1 had a hydroxylated C(1)¼C (2) bond.…”