4-Amino-1-allenylsilanes from 4-Aminopropargylic Acetates through a Silylzincation/Elimination Sequence

In memory to Professor Jean Normant for his outstanding contribution to organometallic chemistry

Abstract

4-Aminopropargylic acetates afford 4-amino-1-allenylsilanes upon reaction with the lithium (triorganosilyl)zincate (PhMe₂Si)₃ZnLi. The reaction is both stereoselective and stereospecific and proceeds through syn-silylzincation of the carbon–carbon triple bond followed by subsequent anti-β-elimination of the acetate group.

Key words

allenes - asymmetric synthesis - diastereoselectivity - silyl­zincation - zincates

• References

• 1 Current address: ESPCI ParisTech, PSL Research University, Laboratoire de Chimie Organique, UMR CNRS 8231, 10 rue Vauquelin, 75231 Paris Cedex 05, France.
• 2 Sakaguchi K, Ohno Y, Oda N, Suzuki H. Tetrahedron Lett. 2010; 51: 3765
• 3 Reginato G, Mordini A, Tenti A, Valacchi M, Broguiere J. Tetrahedron: Asymmetry 2008; 19: 2882
• 4 Bochatay VN, Sanogo Y, Chemla F, Ferreira F, Jackowski O, Pérez-Luna A. Adv. Synth. Catal. 2015; 357: 2809
• 5 For more details, see: Ferreira F, Audouin M, Chemla F. Chem. Eur. J. 2005; 11: 5269

For examples, see:
• 6a Fleming I, Terrett NK. J. Organomet. Chem. 1984; 264: 99
• 6b Borzilleri RM, Weinreb SM, Parvez M. J. Am. Chem. Soc. 1995; 117: 10905
• 6c Urabe H, Takeda T, Hideura D, Sato F. J. Am. Chem. Soc. 1997; 119: 11295
• 7a Chemla F, Ferreira F. Synlett 2006; 2613
• 7b Chemla F, Ferreira F, Gaucher X, Palais L. Synthesis 2006; 1235

The study has been undertaken with racemic α-N-tert-butanesulfinamidoalkyl methoxymethyl ethers 2; however these compounds can also be prepared in enantiomerically pure form. For relevant references, see:
• 8a Ferreira F, Botuha C, Chemla F, Pérez-Luna A. Chem. Soc. Rev. 2009; 38: 1162
• 8b Botuha C, Chemla F, Ferreira F, Louvel J, Pérez-Luna A. Tetrahedron: Asymmetry 2010; 21: 1147
• 9 A sub-stoichiometric amount of (PhMe₂Si)₂Cu(CN)Li₂ (0.9 equiv) was employed at –80 °C in order to avoid nucleophilic attack of the copper species on compound 5a; for a discussion, see ref. 4.
• 10 (PhMe₂Si)₂Cu(CN)Li₂ was prepared as follows: CuCN (17 mg, 0.19 mmol) was introduced into a Schlenk flask and heated for 2 h at 160 °C under vacuum. After cooling to r.t., the Schlenk flask was flushed with argon and anhyd THF (0.12 mL) was added. The resulting suspension of CuCN was cooled to –10 °C prior to a 0.4 M soln of PhMe₂SiLi in THF (0.89 mL, 0.36 mmol) being added dropwise. The reaction mixture was stirred for 30 min, cooled to –80 °C and immediately used.
• 11 Vinylsilane 6b could be isolated and characterized by ¹H NMR, ¹³C NMR and IR spectroscopy, and HRMS.
• 12a Liu J, Cogan DA, Ellman JA. J. Am. Chem. Soc. 1997; 119: 9913
• 12b Chemla F, Ferreira F. J. Org. Chem. 2004; 69: 8244
• 13 Louvel J, Chemla F, Demont E, Ferreira F, Pérez-Luna A, Voituriez A. Adv. Synth. Catal. 2011; 353: 2137
• 14 Colvin EW. Silicon in Organic Synthesis . Butterworths and Co. Ltd; London: 1981: 44

The syn-silylzincation of terminal alkynes promoted by transition-metal catalysts has been shown to give pure E-vinylsilanes upon hydrolysis; see:
• 15a Okuda Y, Wakamatsu K, Tückmantel W, Oshima K, Nozaki H. Tetrahedron Lett. 1985; 26: 4629
• 15b Wakamatsu K, Nonaka T, Okuda Y, Tückmantel W, Oshima K, Utimoto K, Nozaki H. Tetrahedron 1986; 42: 4427
• 15c Nakamura S, Uchiyama M, Ohwada T. J. Am. Chem. Soc. 2004; 126: 11146
• 16 For a recent review on zincate chemistry, see: Uchiyama M, Wang C. Top. Organomet. Chem. 2014; 47: 159
• 17 For recent examples of transition-metal-catalyzed silylzincation of alkynes, see refs. 15, 16, and: Auer G, Oestreich M. Chem. Commun. 2006; 311
• 18 It is worth noting that 1.1 equivalents of SiBNOL–zincate complex reacted sluggishly with 4-aminopropargylic acetate 4a. No reaction occurred at –30 °C in THF, whereas a modest conversion of 35% was observed within 14 h at r.t. affording 4-amino-1-allenylsilane 5a with high stereoselectivity (dr >98:2).
• 19 Suffert J. J. Org. Chem. 1989; 54: 509
• 20 Séguin C, Ferreira F, Botuha C, Chemla F, Pérez-Luna A. J. Org. Chem. 2009; 74: 6986
• 21 Oestreich M, Weiner B. Synlett 2004; 2139