Synlett 2018; 29(01): 126-130
DOI: 10.1055/s-0036-1590876
letter
© Georg Thieme Verlag Stuttgart · New York

A Solvent-Free Reaction for Silyl Enol Ethers Synthesis

Chiara Morozzi, Ornelio Rosati, Massimo Curini, Daniela Lanari*
  • Dipartimento di Scienze Farmaceutiche, Università degli Studi di Perugia, via del Liceo, 1, 06123 Perugia, Italy   Email: daniela.lanari@unipg.it
The authors gratefully thank the Fondazione Cassa di Risparmio di Perugia (Grant no. FCR 2015.0381.021) for supporting the research.
Further Information

Publication History

Received: 22 May 2017

Accepted after revision: 20 July 2017

Publication Date:
22 August 2017 (eFirst)

Abstract

Silyl enol ethers are extremely useful nucleophilic intermediates for chemical transformations because they are synthetically versatile substrates for a wide range of C–C bond-forming reactions. Here, we present a new, mild, and solvent-free procedure for the synthesis of silyl enol ethers that employs a catalytic amount of solid-supported base and an equimolar amount of N,O-(bistrimethylsilyl)acetamide as a silylating agent.

Supporting Information

 
  • References and Notes

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  • 11 Silyl Enol Ethers 3 and 7ao; General Procedure The appropriate aromatic ketone (1.0 mmol), BSA (244 µL, 1.0 mmol), and PS-BEMP (10 mol%, 45 mg or 5 mol%, 22 mg) were added to a vial, and the mixture was stirred at 60 °C for 5 h. The catalyst was filtered off, the mixture was washed with H2O (3 × 2 mL), and the aqueous phase was extracted with hexane (3 × 2 mL). The organic phases were combined, washed with brine (2 mL), dried (Na2SO4), filtered, and concentrated in vacuo to eliminate the acetamide byproduct. The crude mixture was then purified by flash chromatography [silica gel, hexane–Et2O (99:1)] to remove any residual reagent. {[(Z)-2-Bromo-1-(3-nitrophenyl)vinyl]oxy}(trimeth­yl)silane (7k) Yellow oil; yield: 309 mg (98%). 1H NMR (200 MHz, CDCl3): δ = 0.25 (s, 9 H), 6.15 (s, 1 H), 7.52 (t, J = 8 Hz, 1 H), 7.78 (t, J = 4 Hz, 1 H), 8.16 (d, J = 12 Hz, 1 H), 8.31 (s, 1 H). 13C NMR (400 MHz, CDCl3): δ = 1.18, 91.33, 120.76, 123.71, 129.96, 131.48, 138.92, 148.78, 151.65. GC/EIMS: m/z (%) = 315 (18) [M+], 300 (43), 139 (43), 89 (25), 73 (100), 63 (9). Anal. calcd for C11H14BrNO3Si: C, 41.78; H, 4.46; N, 4.43. Found: C, 41.75; H, 4.60; N, 4.32. Silyl enol ethers 7ps, 7v, and 7x: General Procedure The appropriate aliphatic ketone or aldehyde (1.0 mmol), BSA (244 µL, 1.0 mmol), and PS-BEMP (10 mol%, 45 mg) were added to a vial, and the mixture was stirred at 60 °C for the appropriate time. The products were purified by distillation under pressure. (3,6-Dihydro-2H-pyran-4-yloxy)(trimethyl)silane (7s) Colorless oil; yield: 133 mg (77%). 1H NMR (200 MHz, CDCl3): δ = 0.26 (s, 9 H), 2.18–2.22 (m, 2 H), 3.86 (t, J = 5.59 Hz, 2 H), 4.19 (q, J = 2.53, 5.23 Hz, 2 H), 4.87–4.90 (m, 1 H).