[2+2] Cycloaddition of Vinyltrimethylsilane and Dichloroketene and Subsequent Dechlorination; 3-(Trimethylsilyl)cyclobutanone
Submitted Apr 01, 2012, published Apr 06, 2012
Christopher Kelly (email@example.com
A contribution from
Vinyltrimethylsilane (Purchased from Gelest)
Diethyl Ether (CHROMASOLV®, for HPLC, ≥99.9%, inhibitor-free, Sigma-Aldrich)
Zn(Cu) Couple (Prepared in-house from zinc (dust, <10 μm, ≥98%, Sigma-Aldrich) and CuSO4 • 5 H2O (99.999% trace metals basis, purchased from Sigma-Aldrich) according to the procedure of Tilley et al.1 )
Dimethoxyethane, DME ( CHROMASOLV®, for HPLC, 99.9%, Sigma-Aldrich)
Trifluoroacetyl Chloride ( 99% purity, Sigma-Aldrich)
Pentane (anhydrous, ≥99%, Sigma-Aldrich
Saturated Sodium Bicarbonate Solution
Na2SO4 (ACS reagent, ≥99.0%, anhydrous, granular, Sigma-Aldrich)
Step 1 : [2+2] Cycloaddition2,3
To a one-necked, 2L round bottom flask equipped with stir bar was placed was added 50.0 g (0.765 mol, 1.53 equiv) of zinc-copper couple. The flask was then equipped with 500 mL addition funnel with a gas inlet adapter, The flask was then flushed with nitrogen. To this flask was added 50.0 g (0.499 mol, 1 equiv) of vinyltrimethylsilane in distilleda Et2O (625mL, 0.8 M in vinyltrimethylsilane). The closed addition funnel was then charged with 102.8 g (63.5 mL, 0.565 mol, 1.13 equiv) of trichloroacetyl chlorideb distilleda DME (375 mL,1.51 M in trichloroacetyl chloride ). The mixture in the addition funnel was stirred using a glass stirring rod to ensure homogeneity . The resulting solution was added dropwise to the vigorously stirred solution in the flask over a period of 6 hours. Following this addition, the mixture was allowed to stir for 66 hours whereupon it became a dark-brown color and the remaining suspended zinc-copper couple had a whitish hue.
Step 2: Dechlorination4
The reaction mixture was cooled to 0 oC in an ice bath. While still stirring vigorously, the addition funnel was charged with 125 mL (6.94 mol, 13.9 equiv) of deionized water and was then added dropwise over a period of 45 minutes. The addition funnel was removed and replaced with an N2 inlet adapter. At five minute intervals, the nitrogen inlet was removed and scoops (roughly 5-10 g per scoop) of fresh zinc-copper couple was added until a total of 100 g (1.53 mol, 3.07 equiv) had been added over a period of 1 hour. At this point, the ice in the bath had meltedc, the water in the bath was noted to be warmer than room temperature (approximately 30 °C). The solution was re-cooled and allowed to react for an additional 20 hours as it warmed to room temperature. At this time, solvent layer above the zinc-copper slurry was decanted through a medium sintered glass funnel under vacuum. Celite® was then added into the funnel and the remaining material including the zinc was then poured through the funnel eluting with 150 mL of ether. The residual solid was rinsed with an additional 100 mL of ether.
Because of the large volume of liquid, the filtrate was divided into two portions.d The first portion was washed with brine (3 X 150 mL). The combined brine layers were then extracted with pentane (1 X 150 mL), which was recombined with the organic layer. The organic layer was then washed with saturated NaHCO3 (3 X 150 mL) and deionized H2O (1 X 200 mL). This entire process was repeated for the second portion of the filtrate. The combine organic layers were dried via anhydrous Na2SO4 and the solvent was removed by rotary evaporation under aspirator vacuum in a 30°C water bathe. The residual was then fractionally distilled under vacuum through a 10 cm Vigreaux column (bp 75-78 °C @ 30 mm Hg) giving the cyclobutanone as a colorless liquid (26.5 g, 37.5% over two steps).
1H NMR (CDCl3, 300 MHz): δ 0.005 ppm (9H, s), 1.45-1.58 (1H, m) 2.76-2.86 (2H, m), 3.08-3.18 (2H, m);
13C NMR (CDCl3 75 MHz) δ -3.69 (CH3), 9.03 (CH), 48.53 (CH2), 207.86 (C);
GC-MS (EI) 142 ([M]+, 0.003%) 141 ([M-H]+, 0.008%), 127 ([M-CH3]+, 1.6%), 114 (5.9%), 85 (16.9%) 73 (100%), 59 (12%), 45 (14%), 43 (13%).
Boiling Point: 75-78 °C @ 30 mm Hg
1. Kelly, C. B.; Colthart, A. M.; Constant, B.D.; Corning, S.R.; Dubois, L. N. E.; Genovese, J. T.; Radziewicz, J. L.; Sletten, E. M.; Whitaker, K. R.; Tilley, J. J. Org. Lett.2011, 13, 1646.
2. R. Danheiser, H. Sard, Tetrahedron Lett. 1983, 24, 23.
3. A. Hassner, J. L. Dillion, Jr., J. Org. Chem. 1983, 48, 3382-3386.
4. M. Murakami, U. Ippei, M. Hasegawa, T. Matsuda, J. Am. Chem. 2005, 127, 1366-1367.
1H NMR (hnmr cyclobutanone.jpg)
13C NMR (c13 nmr cyclobutanone.jpg)
e.g. Actual NMR spectra (as images or jdx files for interactive spectra), photographs of apparatus, TLC’s or crystals or videos. Please contact the ChemSpider team (ChemSpider-at-rsc.org) for help with this.
Keywords: [2+2] Cycloaddition, addition, Alkanes, alkyl/alkenyl/aryl halides, carbocyclic compounds, Cyclobutanes, Dehalogenation, ketones, Organosilicon, Small Ring Compounds