Synlett 2017; 28(18): 2449-2452
DOI: 10.1055/s-0036-1590902
cluster
© Georg Thieme Verlag Stuttgart · New York

A Quantitative NMR Method for Silyllithium Analysis

Yingjian Bo
Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, USA   Email: scott.sieburth@temple.edu
,
Scott McN. Sieburth*
Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, USA   Email: scott.sieburth@temple.edu
› Author Affiliations
This work was supported by the National Institute of General Medical Sciences (grant number R01GM076471).
Further Information

Publication History

Received: 14 August 2017

Accepted after revision: 17 August 2017

Publication Date:
05 September 2017 (eFirst)

Published as part of the Cluster Silicon in Synthesis and Catalysis

Abstract

A rapid and extremely simple method for silyl anion analysis is presented. The progress of silyllithium reagent preparation can be determined by quenching an aliquot with neat chloro(trimethyl)silane, evaporation, dilution with CDCl3, and direct proton NMR analysis. This procedure is fast, simple, and allows for identification and relative quantification of the starting reagent, intermediates, and the silyllithium product.

Supporting Information

 
  • References and Notes

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  • 43 1-[3-(Methoxymethoxy)propyl]-2,2,2-trimethyl-1,1-diphenyldisilane (11) Granular lithium shot [87 mg, 12.5 mmol, 14 equiv, in mineral oil (Aldrich)] was washed three times with hexane then transferred to a 25 mL round-bottomed flask fitted with a septum. The flask was evacuated and then filled with argon three times. THF (6 mL) was added, and the mixture cooled to 0 °C. TMSCl (0.3 mL) was then added, the mixture was stirred for 30 min, and the solution was removed by syringe. The cleaned lithium shot was washed with THF (3 × 3 mL). A solution of [3-(methoxymethoxy)propyl](diphenyl)silane (10; 259 mg, 0.90 mmol) in THF (3.0 mL) was added, and the mixture was stirred for 9 h. The solution was decanted and washed with H2O. The aqueous phase was extracted with Et2O (3 × 10 mL), and the combined organics were dried (Na2SO4, filtered, and concentrated. Purification by flash chromatography (gradient 100:1 to 10:1 hexanes–EtOAc) gave a clear, colorless oil; yield: 214 mg (60%); Rf = 0.53 (4:1 hexanes–EtOAc). IR (neat): 3067, 2947, 2086, 1954, 1428 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.45–7.50 (m, 4 H), 7.32–7.37 (m, 6 H), 4.60 (s, 2 H), 3.50 (t, J = 6.6 Hz, 2 H), 3.34 (s, 3 H), 1.64–1.73 (m, 2 H), 1.17–1.24 (m, 2 H), 0.17 (s, 9 H). 13C NMR (125 MHz, CDCl3): δ = 136.3, 135.4, 128.9, 128.0, 96.5, 70.7, 55.3, 25.1, 9.1, –1.1. HRMS: m/z [M + NH4]+ calcd for C20H34NO2Si2: 376.2123; found: 376.2123.
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