The development of methodologies for carbon Γ carbon bond formation by deoxygenation of the CO moieties in carbonyl compounds has attracted much attention as a powerful synthetic strategy. [1] In general, two types of CΓC bond-forming reactions that involve the deoxygenation of CΓO double bonds in carbonyl compounds are known (Scheme 1, Type I and Type II). Type I reactions give rise to a C Γ C double bond. The Wittig-type reactions, [2] Tebbes reagent or Grubbs titanacycle, [3] and the McMurry reaction [4] have been utilized extensively to convert carbonyl compounds into alkenes. Type II reactions form two C(sp 3 )ΓC(sp 3 ) bonds. Reetzs direct geminal dialkylation, which uses organotitanium reagents [5] and AlMe 3 , [6] and direct geminal diallylation, which uses vanadium(ii) species [7] have been reported. We stereogenic center and with high levels of regio-and acyclic stereocontrol. Additionally, a synthetically useful b-dicarbonyl functionality is introduced.
Experimental Section
Compound (AE)-5: (AE)-1 (402 mg, 1.0 mmol) and ethyl acetoacetate (156 mg, 1.2 mmol) were added sequentially to a solution of [RhH(CO)(PPh 3 ) 3 ] (9.2 mg, 1 Γ 10 Γ2 mmol) in toluene (3 mL) at 20 8C (with exclusion of air and moisture). The solution was stirred for 5 min and then piperidine (17 mg, 0.2 mmol) and acetic acid (12 mg, 0.2 mmol) were added sequentially. The resulting solution was transferred by cannula (rinsed with 2 mL of toluene) into an evacuated and argon-filled stainlesssteel autoclave. The autoclave was heated to 90 8C and pressurized with 20 bar H 2 /CO (1:1). After stirring for 24 h at this temperature the autoclave was cooled rapidly to 20 8C and depressurized. The reaction solution was filtered through a small pad of silica with tert-butylmethylether (50 mL). After evaporation of the solvent, the crude product was analyzed by NMR spectroscopy to determine the diastereomeric ratio (syn/anti 96:4). Subsequent purification by column chromatography on silica with petroleum ether (40/60)/tert-butylmethylether (4:1) provided the b-ketoester (AE)-5 (390 mg, 71 %) as a highly viscous oil. 1 H NMR (500.130 MHz, CDCl 3 , 258C, TMS): d 0.77 Β± 0.87 (m, 9 H), 1.05 Β± 1.10 (m, 1 H), 1.24 (m c , 3 H), 1.69 Β± 1.92 (m, 5 H), 2.15 [2.18] (s, 3 H), 3.24 [3.30] (pt, J 7.3 Hz, 1 H), 4.11 Β± 4.21 (m, 2 H), 4.81 (m c , 1 H), 6.91 (m c , 1 H), 7.25 Β± 7.31 (m, 10 H), 7.38 (m c , 2 H), 8.08 (m c , 1 H); 13 C NMR (125.758 MHz, CDCl 3 , 258C): d 13.7 [13.8], 14.0, 18.2 [18.4], 19.1 [19.2], 25.6 [25.7], 28.7 [29.0], 29.5, 31.2 [31.4], 34.3, 56.6 [59.9], 61.2 [61.3], 81.5 [81.8], 128.1 (d, 3 J C,P 2.8 Hz), 128.4 (d, 3 J C,P 6.9 Hz, 2 C), 128.4 Β± 128.5 (2 C), 130.4, 131.8 (d, 3 J C,P 6.4 Hz), 133.7 Β± 134.3 (8 C), 138.1 Β± 138.3 (2 C), 140.9 (d, 1 J C,P 28.2 Hz) [141.0 (d, 1 J C,P 27.6 Hz)], 166.30 [166.32], 169.6 [169.7], 203.2 [203.3]; 31 P NMR (202.457 MHz, CDCl 3 , 258C, 85 % H 3 PO 4 ): d Γ 4.49 (s) [Γ 4.51 (s)]; elemental analysis: calcd. (%) for C 33 H 39 O 5 P: C 72.51, H 7.19; found C 72.62, H 7.34.