Preparation of Cyclopropylsilanes from Terminal Alkenes with Organo­chromium Reagents

Abstract

Treatment of terminal alkenes with Me₃SiCHI₂, CrCl₂, and TMEDA in THF at 25 °C gives cyclopropylsilanes in good to excellent yields. The trans:cis ratios of the cyclopropylsilanes are improved by replacing Me₃SiCHI₂ with i-Pr₃SiCHBr₂ and LiI.

Key words

chromium(II) - cyclopropylsilane - cyclopropane

References

• 1a Weber WP. Silicon Reagents for Organic Synthesis   Springer-Verlag; Berlin: 1983.  p.159-163  
• 1b Paquette LA. Chem. Rev.  1986,  86:  733 
• 1c Krief A. Top. Curr. Chem.  1987,  135:  1 
• 2a Seyferth D. Cohen HM. Inorg. Chem.  1962,  1:  913 
• 2b Sternberg E. Binger P. Tetrahedron Lett.  1985,  26:  301 
• 2c Ahra M. Grignon-Dubois M. Dunoguès J. J. Organomet. Chem.  1984,  271:  15 
• 2d Tamao K. Nakajima T. Kumada M. Organometallics  1984,  3:  1655 
• 2e Olofson RA. Hoskin DH. Lotts KD. Tetrahedron Lett.  1978,  1677 
• 2f Seyferth D. Dow AW. Menzel H. Flood TC. J. Am. Chem. Soc.  1968,  90:  1080 
• 2g Ashe AJ. J. Am. Chem. Soc.  1973,  95:  818 
• 2h Taylor RT. Paquette LA. J. Org. Chem.  1978,  43:  242 
• 3a Takai K. Kataoka Y. Okazoe T. Utimoto K. Tetrahedron Lett.  1987,  28:  1443 
• 3b Takai K. Hikasa S. Ichiguchi T. Sumino N. Synlett  1999,  1769 
• 3c Hodgson DM. Comina PJ. Drew MGB. J. Chem. Soc., Perkin Trans. 1  1997,  2279 
• 4 Takai K. Toshikawa S. Inoue A. Kokumai R. J. Am. Chem. Soc.  2003,  125:  12990 
• 5 Villieras J. Bacquet C. Normant JF. Bull. Soc. Chim. Fr.  1976,  1797 
• 6a Oxidation of 5 with pyridinium chlorochromate produced the corresponding ketone in 83% yield, which was identical to the ketone in the following literature: Ramig K. Bhupathy M. Cohen T. J. Org. Chem.  1989,  54:  4404 
• 6b

  The structure of 5 was also confirmed by X-ray crystallography.

• 7 A chromium-alkylidene complex having a TMEDA ligand was isolated, see: Hao S. Song J.-I. Berno P. Gambarotta S. Organometallics  1994,  13:  1326 
• 8 Silyl-substituted dizinciomethanes can be prepared by reduction of R₃SiCHBr₂ with zinc in the presence of PbCl₂. See: Matsubara S. Otake Y. Morikawa T. Utimoto K. Synlett  1998,  1315 
• 10 Lee JB. Gajda GJ. Schaefer WP. Howard TR. Ikariya T. Straus DA. Grubbs RH. J. Am. Chem. Soc.  1981,  103:  7358 

9

The geminal dichromium reagent was generated by stirring Me₃SiCHI₂ (1.0 mmol) and CrCl₂ (4.0 mmol) in THF at 25 °C for 1 h (Scheme [2] ). Treatment of 3-phenylpropanal (2.0 mmol) with the reagent gave trimethyl(4-phenyl-1-butenyl)silane in 75% yield (E:Z = >99:<1) after stirring at 25 °C for 4 h; the aldehyde was recovered in 47% yield. [3b] In contrast, when TMEDA (4.0 mmol) was added to the geminal dichromium reagent generated at 25 °C for 1 h and the mixture was stirred for a further 15 min, treatment of allyl benzyl ether (2.0 mmol) with the base-added reagent at 25 °C for 4 h gave 1a in 70% yield (based on Me₃SiCHI₂, trans:cis = 68:32) along with unreacted allyl benzyl ether in 63% yield (Scheme [2] ). These results suggest that the reactive species of the silylcyclopropanation is not a carbenoid but the species derived from 6 and TMEDA.

11

When the reaction was conducted with allyl benzyl ether (2.0 mmol), Me₃SiCHI₂ (1.0 mmol), CrCl₂ (2.0 mmol), and TMEDA (2.0 mmol), the yield was still 60% based on Me₃SiCHI₂ (trans:cis = 68:32), and allyl benzyl ether was recovered in 62% yield. The comproportionation reaction of both 1 equiv of CrX₃ and CrX generating 2 equiv of CrX₂ could reduce the amount of the required CrCl₂.