C–C bond migration in the cycloisomerization of 1,6-enynes

Abstract

A full account of our investigation of C–C bond migration in the cycloisomerization of oxygen-tethered 1,6-enynes is described. Under Pt(II) and/or Ir(I) catalysis, cyclic and acylic alkyl groups were found to undergo 1,2-shifts into metal carbenoid intermediates. Interestingly, this process does not appear to be driven by the release of ring strain, and thus provides access to large carbocyclic frameworks. The beneficial effect of CO on the Pt(II) and Ir(I) catalytic systems is also evaluated.

Rh‐Catalyzed Reaction of Propargylic Alcohols with Aryl Boronic Acids–Switch from β‐OH Elimination to Protodemetalation

“…NMR spectra were taken with an Agilent‐400 spectrometer or Bruker Avance III spectrometer (400 MHz for H NMR, 100 MHz for C NMR, 376 MHz for F NMR) in CDCl 3 . All H NMR experiments were measured with tetramethylsilane ( δ 0) in CDCl 3 as the internal reference; C NMR experiments were measured in relative to the signal of CDCl 3 ( δ 77.0); F NMR experiments were measured in relative to the signal of CFCl 3 ( δ 0) in CDCl 3 . [Cp*RhCl 2 ] 2 was purchased from Sinocompound and J&K; AgBF 4 was purchased from Acros and Strem; NaOAc was purchased from Macklin and Sinopharm Chemical Reagent Co., Ltd.; B(OH) 3 was purchased from Sinopharm Chemical Reagent Co., Ltd.; n BuLi (2.5 mol·L –1 in Hexane) was purchased from Infinity Scientific.…”

“…Following Typical Procedure II , the reaction of AgBF 4 (29.5 mg, 0.15 mmol), [Cp*RhCl 2 ] 2 (15.5 mg, 0.025 mmol), NaOAc (16.4 mg, 0.20 mmol), 2c (214.2 mg, 1.5 mmol), 1a (140.3 mg, 1.0 mmol), and MeOH (5 mL) afforded E ‐3ac (171.9 mg, 73%) (11% of 1a remained which was determined by H NMR analysis of the crude product using dibromomethane as an internal standard) [eluent: toluene (500 mL)]: light yellow oil; H NMR (400 MHz, CDCl 3 ) δ : 7.31—7.20 (m, 2H, Ar‐H), 7.04—6.92 (m, 2H, Ar‐H), 5.64 (s, 1H, =CH), 2.78 (t, J = 7.6 Hz, 2H, CH 2 ), 1.61 (brs, 1H, OH), 1.46 (s, 6H, 2 x CH 3 ), 1.36—1.18 (m, 4H, 2 x CH 2 ), 0.84 (t, J = 7.0 Hz, 3H, CH 3 ); C NMR (100 MHz, CDCl 3 ) δ : 161.9 (d, J = 243.6 Hz), 142.1, 139.7 (d, J = 3.0 Hz), 135.8, 128.1 (d, J = 7.6 Hz), 114.9 (d, J = 20.5 Hz), 71.3, 31.6, 31.0, 29.8, 22.9, 13.9; F NMR (376 MHz, CDCl 3 ) δ : –116.8; IR (neat) v : 3357, 2961, 2928, 2861, 1637, 1601, 1506, 1465, 1362, 1220, 1157, 1106, 1014 cm –1 ; MS (70 eV, EI) m / z (%): 236 (M + , 4.74), 109 (100); HRMS calcd for C 15 H 21 FO [M + ]: 236.1576, found: 236.1582.…”

“…Following Typical Procedure II , the reaction of AgBF 4 (29.5 mg, 0.15 mmol), [Cp*RhCl 2 ] 2 (15.5 mg, 0.025 mmol), NaOAc (16.4 mg, 0.20 mmol), 2k (290.7 mg, 1.5 mmol), 1a (140.3 mg, 1.0 mmol) and MeOH (5 mL) afforded E ‐ 3ak (260.1 mg, 91%) [eluent: petroleum ether/dichloromethane = 1/1 (500 mL)]: light yellow oil; H NMR (400 MHz, CDCl 3 ) δ : 7.63 (d, J = 8.0 Hz, 1H, Ar‐H), 7.45 (t, J = 7.4 Hz, 1H, Ar‐H), 7.34 (t, J = 7.6 Hz, 1H, Ar‐H), 7.21 (d, J = 7.6 Hz, 1H, Ar‐H), 5.41 (s, 1H, =CH), 2.75—2.62 (m, 2H, CH 2 ), 1.62 (s, 1H, OH), 1.44 (s, 6H, 2 x CH 3 ), 1.35—1.21 (m, 4H, 2 x CH 2 ), 0.84 (t, J = 6.8 Hz, 3H, CH 3 ); C NMR (100 MHz, CDCl 3 ) δ : 143.5 (q, J = 2.0 Hz), 140.4, 137.3, 130.9, 130.7, 128.0 (q, J = 29.3 Hz), 126.6, 126.2 (q, J = 5.3 Hz), 124.4 (q, J = 272.7 Hz), 71.4, 32.1, 31.1, 30.6, 23.1, 13.9; F NMR (376 MHz, CDCl 3 ) δ : –57.5; IR (neat) v : 3399, 2962, 2931, 2862, 1604, 1575, 1448, 1311, 1168, 1112, 1061, 1034 cm –1 ; MS (ESI) m / z (%): 269 (M‐OH) + ; HRMS calcd for C 16 H 21 F 3 O [M + ]: 286.1545, found: 286.1535.…”

“…After 25 h, the resulting mixture was filtered through a short column of celite (3 cm) eluted with MeOH (15 mL), and concentrated. The mixture was purified by column chromatography on silica gel to afford ( R )‐ E ‐ 3fi (115.2 mg, 83%, 97% ee) [eluent: petroleum ether/dichloromethane/diethyl ether = 20/1/1 (800 mL)]: light yellow oil; HPLC conditions: AD‐H column, hexane/ i ‐PrOH = 95/5, 0.8 mL/min, λ = 214 nm, t R (minor) = 9.0 min, t R (major) = 9.8 min; [α] D = –43.36 ( c = 1.24, CHCl 3 ); H NMR (400 MHz, CDCl 3 ) δ : 7.55 (t, J = 9.0 Hz, 4H, Ar‐H), 7.42 (d, J = 8.0 Hz, 2H, Ar‐H), 7.34 (t, J = 7.8 Hz, 2H, Ar‐H), 7.29—7.19 (m, 1H, Ar‐H), 6.14 (s, 1H, =CH), 2.50—2.35 (m, 2H, CH 2 ), 2.05 (brs, 1H, OH), 1.74 (s, 3H, CH 3 ), 1.08—0.79 (m, 4H, 2 x CH 2 ), 0.66 (t, J = 7.0 Hz, 3H, CH 3 ); C NMR (100 MHz, CDCl 3 ) δ : 148.4, 146.8, 143.9, 137.4, 129.1 (q, J = 31.1 Hz), 128.2, 127.0, 126.7, 125.2 (q, J = 3.8 Hz), 125.1, 124.3 (q, J = 270.5 Hz), 74.2, 33.6, 30.0, 29.8 , 22.7, 13.7; F NMR (376 MHz, CDCl 3 ) δ : –62.9; IR (neat) v : 3445, 2961, 2928, 2865, 1614, 1452, 1321, 1163, 1117, 1064, 1017 cm –1 ; MS (70 eV, EI) m / z (%): 348 (M + , 1.90), 134 (100); HRMS calcd for C 21 H 23 F 3 O [M + ]: 348.1701, found: 348.1700.…”

Gold(I)‐Catalyzed Ring Expansion of Alkynylcyclopropyl Allyl Ethers to Construct Tetrasubstituted Methylenecyclobutanones: A Mechanistic Investigation about the Character of Catalytic Amount of Water

“…[8b,e] Later in 2012, Fensterbank and coworkers discovered a gold-catalyzed cycloisomerization of O-tethered 1,6-enynes to produce naturalproduct-like macrocycles (Scheme 1b). [11] During our ongoing investigations on the chemical transformation of strained small rings, [12] we envisioned that introducing a highly strained cyclopropane ring into enyne's backbone might lead to an interesting ring expansion consequence to give functionalized four-memberedring scaffolds. Inspired by this working hypothesis, various enynes bearing cyclopropane moiety were synthesized and we found that some of them exhibited unique chemical reactivities.…”