Spiranes synthesis based on samarium diiodide-mediated reductive cyclization

Asymmetric Total Syntheses of (+)-5-epi-Schisansphenin B and the Proposed Structure of (+)-15-Hydroxyacora-4(14),8-diene

“…After the synthesis of enone-aldehyde 5 , the next step was the construction of the spiro skeleton. Compound 5 was first treated with samarium diiodide, followed by oxidation with pyridinium chlorochromate (PCC) to obtain the desired spirocyclic 1,4-dione in 48% overall yield as a 1:1 mixture of inseparable diastereoisomers (Scheme ). To improve diastereoselectivity, we used acyl radical cyclization .…”

Construction of Spirofused Tricyclic Frameworks by NHC-Catalyzed Intramolecular Stetter Reaction of a Benzaldehyde Tether with a Cyclic Enone

“…Chromatography (EtOAc/hexanes = 1:10); white solid; 9.69 g; yield 93%; mp 54− 55 °C; IR (neat) ν: 3380,3026,2930,2856,2163,1446,1250,1025,843, 759 cm −1 ; 1 H NMR (400 MHz, CDCl 3 ): δ 5.80−5.70 (m, 2H), 2.27−2.12 (m, 2H), 2.06 (br s, 1H), 1.97−1.82 (m, 4H), 1.79−1.70 (m, 1H), 1.49−1.40 (m, 1H), 0.17 (s, 9H); 13 C{ 1 H} NMR (100 MHz, CDCl 3 ): δ 137. 4, 131.4, 107.5, 89.0, 71.4, 41.0, 27.4, 26.7, 25.6, −0.1; MS (EI) m/z (% base peak): 208 (M + , 5), 191 (100), 175 (3), 163 (3), 147 (2), 135 (5), 117 (10), 111 (7), 97 (7), 73 (29); HRMS (EI-TOF) m/z: [M] + calcd for C 12 H 20 OSi, 208.1283;found, 208.1280.…”

“…2-[(3-Oxocyclohex-1-en-1-yl)ethynyl]benzaldehyde (7ab). Chromatography (EtOAc/hexanes = 1:5); yellow solid; 413 mg; yield 92%; mp 59−60 °C; IR (neat) ν: 3065,2948,2743,2202,1697,1671,1590,1190, 765 cm −1 ; 1 H NMR (400 MHz, CDCl 3 ): δ 10.41 (s, 1H), 7.87 (d,J = 7.8 Hz,1H),2H),1H),6.27 (t,J = 1.6 Hz,1H), 2.53 (dt, J = 6.1, 1.6 Hz, 2H), 2.41 (t, J = 6.8 Hz, 2H), 2.07−2.01 (m, 2H); 13 C{ 1 H} NMR (100 MHz,CDCl 3 ): δ 198.4,190.9,142.1,136.0,133.9,133.5,133.3,129.8,127.8,125.0,94.6,94.5,37.3,30.2,22.6; MS (EI) m/z (% base peak): 224 (M + , 67), 206 (11), 196 (28), 181 (21), 168 (100), 167 (31), 139 (71), 126 (9), 89 (5); HRMS (EI-TOF) m/z: [M] + calcd for C 15 H 12 O 2 , 224.0837; found, 224.0834.…”

“…Consequently, the development of new and efficient strategies for constructing the spiro core has become a major focal point for synthetic chemistry . Recently, we developed intramolecular cyclizations of enone-aldehydes via samarium diiodide-mediated reductive cyclization and thiol-mediated acyl radical cyclization to prepare spirocyclic γ-hydroxyketones and 1,4-diketones, respectively (Scheme ). As a continuation of our work, we report here the intramolecular Stetter reaction of benzaldehyde tethers with a cyclic enone to construct various spirofused tricyclic 1,4-diketones.…”

Cross-Coupling Reactions Using Samarium(II) Iodide

“…Hsu reported a related SmI 2 -mediated cross-coupling of β-tethered aldehydes onto cyclic enones to yield spirocyclic alcohols in good yields and modest stereoselectivity (Scheme ) . The best results in terms of yield and diastereoselectivity were obtained using the SmI 2 –MeOH system at 0 °C.…”