t-Butyldimethylsilyl Ethylnitronate

[77242-15-0]  · C8H19NO2Si  · t-Butyldimethylsilyl Ethylnitronate  · (MW 189.33)

(reagent for diastereoselective nitro-aldol condensations;1 dipole in thioaldehyde [2 + 3] cycloadditions;2 oxygen source for thioketone to ketone conversion;3 oxidative coupling with silyl enol ethers4)

Physical Data: bp 30 °C/0.05 mmHg.1b

Solubility: sol THF.

Form Supplied in: colorless oil. Drying: similar trimethylsilyl derivatives are water sensitive.5

Preparative Method: must be synthesized from Nitroethane.5

Handling, Storage, and Precautions: this reagent is presumed to be moisture sensitive; the hydrolysis product is nitroethane. All nitro compounds should be treated with caution. Use in a fume hood.

Nitro-Aldol Condensation.

Nitro-aldol condensations of t-butyldimethylsilyl ethylnitronate (1) with aldehydes give the erythro isomer almost exclusively (eq 1).1 The silylnitronate must be distilled, the Tetra-n-butylammonium Fluoride (TBAF) must be freshly dried over molecular sieves, and the reaction time must not be too long or else the diastereoselectivity may be compromised.1b The nitroaldol (2) may also be obtained by deprotonation/reprotonation of a mixture of (2) and its diastereomer, but -100 °C is required to achieve high diastereoselectivity in this reaction. For the nitro-aldol reaction the t-butyldimethylsilyl nitronates are less labile and more selective than the trimethylsilyl derivatives.

1,3-Dipole in [3 + 2] Cycloadditions.

t-Butyldimethylsilyl ethylnitronate has been used as a highly reactive dipole to trap thiopivaldehyde (4) (R = t-Bu)2a,b and other reactive thioaldehydes (4) (eq 2),2c which are generated by photolysis of phenacyl sulfides (3), to give heterocycles (5) (Table 1). Use of this reagent to titrate thioaldehyde solutions has also been demonstrated.2d

Other more complex phenacyl sulfides have been photolytically cleaved to thioaldehydes and trapped with (1),2e culminating with its use as a dipole in the total synthesis of (±)-methynolide (eq 3).3 A thiocarbonyl to carbonyl conversion is the end result of the transformation using this reagent.

Oxidative Coupling.

Oxidative coupling of t-butyldimethylsilyl ethylnitronate with a silyl enol ether in DMF using manganese(III) pyridinecarboxylate [Mn(pic)3] as the reducing agent gives an enone after elimination of nitrous acid (eq 4).4

Related Reagents.


1. (a) Seebach, D.; Beck, A. K.; Lehr, F.; Weller, T.; Colvin, E. AG(E) 1981, 20, 397. (b) Seebach, D.; Beck, A. K.; Mukhopadhyay, T.; Thomas, E. HCA 1982, 65, 1101.
2. (a) Vedejs, E.; Perry, D. A. JACS 1983, 105, 1683. (b) Vedejs, E.; Wilde, R. G. JOC 1986, 51, 117. (c) Vedejs, E.; Perry, D. A.; Houk, K. N.; Rondan, N. G. JACS 1983, 105, 6999. (d) Vedejs, E.; Perry, D. A.; Wilde, R. G. JACS 1986, 108, 2985. (e) Vedejs, E.; Perry, D. A. JOC 1984, 49, 573.
3. Vedejs, E.; Buchanan, R. A.; Watanabe, Y. JACS 1989, 111, 8430.
4. Narasaka, K.; Iwakura, K.; Okauchi, T. CL 1991, 423.
5. Colvin, E. W.; Beck, A. K.; Bastani, B.; Seebach, D.; Kai, Y.; Dunitz, J. D. HCA 1980, 63, 697.

Thomas J. Fleck

The Upjohn Company, Kalamazoo, MI, USA

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