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[2+2] Cycloaddition of Vinyltrimethylsilane and Dichloroketene and Subsequent Dechlorination; 3-(Trimethylsilyl)cyclobutanone

SyntheticPage 552
DOI: 10.1039/SP552
Submitted Apr 01, 2012, published Apr 06, 2012
Christopher Kelly (christopher.b.kelly@uconn.edu)
A contribution from Tilley Group


			Reaction Scheme: <IMG src="/images/empty.gif">[2+2] Cycloaddition of <SPAN id=csm1378729728830 class=csm-chemical-name title=Vinyltrimethylsilane grpid="1">Vinyltrimethylsilane</SPAN> and <SPAN id=csm1378729750948 class=csm-chemical-name title=Dichloroketene grpid="2">Dichloroketene</SPAN> and Subsequent Dechlorination<IMG src="/images/empty.gif">

Chemicals Used

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
Brine
Saturated Sodium Bicarbonate Solution 
Na2SO4 (ACS reagent, ≥99.0%, anhydrous, granular, Sigma-Aldrich) 

Procedure

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). 

Author's Comments

Notes:
a. Distillation removes any other impurities that may be present, such as ethanol or BHT, when lower purity ethereal samples were used
b. CAUTION: Toxic, Corrosive, and a very potent lachrymator
c. This reaction is likely exothermic, hence the slow addition of the zinc copper couple 
d. This was because large enough glassware was not available to use to do the workup all at once. If such glassware is available, it is recommended that this be done as a non-portion wise. 
e. CAUTION: The product is somewhat volatile so care must be taken when removing the solvent under vacuum  

Data

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


Lead Reference

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.201113, 1646.

Other References

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.

Supplementary Information

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.
1H NMR (hnmr cyclobutanone.jpg)
13C NMR (c13 nmr cyclobutanone.jpg)

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Keywords: [2+2] Cycloaddition, addition, Alkanes, alkyl/alkenyl/aryl halides, carbocyclic compounds, Cyclobutanes, Dehalogenation, ketones, Organosilicon, Small Ring Compounds

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