Asymmetric synthesis. Part 6. Copper salt promoted grignard reagent additions to ethyl 2,3-dideoxy-4,5:6,7-di-O-isopropylidene-D-arabino-trans-hept-2-enonate and subsequent formation of optically active 2-alkyl (or aryl) butane-1,4-dioic acids and butyro-1,4-lactones

Abstract

The copper-salt promoted 1,4-additions of aryl and t-butyl Grignard reagents to ethyl 2,3-dideoxy-4,5:6,7-di-O-isopropylidene-~-arabino-trans-hept-2-enonate are highly stereoselective yielding products with the D-manno-configuration. In contrast isopropyl and ethyl Grignard reagents give products preponderantly with the D-gluco-configuration. Cyclohexylmagnesium bromide does not react stereoselectively but gives a 55 : 45 mixture of the D -~~U C O -and D-manno-isomers. Controlled degradation of the carbohydrate molecule affords 2-aryl (alkyl) butane-I ,4-dioic acids and 3-aryl (alkyl) -butyro-I ,4lactones. The enantiomeric purity of these products is established by reference to known products or by use of optically active n.m.r. shift reagents.

Enantioselective Baeyer–Villiger Oxidation Catalyzed by Palladium(II) Complexes with Chiral P,N-Ligands

“…Yield 81.9 mg, 93%; [α] 24 D +36.9 ( c 1.0, CHCl 3 , 75% ee); 1 H NMR (400 MHz, CDCl 3 ) δ 2.34 (s, 3H, CH 3 ), 2.65 (dd, J = 17.5, 8.9 Hz, 1H, 2-H), 2.90 (dd, J = 17.5, 8.9 Hz, 1H, 2-H′), 3.75 (pent, J = 8.9 Hz, 1H, 3-H), 4.23 (dd, J = 8.9, 8.0 Hz, 1H, 4-H), 4.64 (dd, J = 8.9, 8.0 Hz, 1H, 4-H′), 7.11 (d, J = 8.1 Hz, 2H, 3′-H, 5′-H), 7.17 (dd, J = 8.1 Hz, 2H, 2′-H, 6′-H); 13 C NMR (100 MHz, CDCl 3 ) δ 21.0 (CH 3 ), 35.7 (CH 2 -2), 40.8 (CH-3), 74.1 (CH 2 -4), 126.5 (2 × CH-3′,5′), 129.7 (2 × CH-2′,6′), 136.3 (C-1′), 137.4 (C-4′), 176.4 (CO) in agreement with the literature data; Chiral GC (Supelco α-DEX), carrier gas, He (flow 2 mL·min −1 ), injection temp 200 °C, initial column temp 110 °C for 3 min, rate 1 deg·min −1 , final temp 220 °C, t R = 66.18 min, t S = 66.67 min.…”

Enantioseparation of 2‐(4‐chlorophenyl)succinic acid by countercurrent chromatography and investigation of injection volume on resolution

“…2‐(4‐Chlorophenyl)succinic acid can be used for preparation of 2‐(4‐chlorophenyl)succinic butanedioate [23]. Succinic acid derivatives and their esters have been traditionally used for numerous applications in preparation of polymers [24] and lubricants where the packing of the aliphatic chains has been used to modify the physical and chemical properties of the polymeric systems.…”

Rhodium(II)-Catalyzed C–H Functionalization of Electron-Deficient Methyl Groups

“…Ozonolysis of 3b generated the aldehyde 20 in 86% yield. Pinnick–Lindgren–Kraus oxidation of 20 followed by TCE deprotection generated the known succinic acid derivative 21 , and this compound was used to determine the absolute configuration of 21 by comparison of its optical rotation with the reported value …”