The di-Grignard Reagent of o-bis Chloromethyl benzene

All operations including those in Sections B and C should be carried out in an atmosphere of purified nitrogen and solvents should be free from oxygen or moisture. Magnesium powder (1.20 g, 49 mmol) (May and Baker or Alpha, 50 mesh) is placed in a dry 500-mL three-necked flask equipped with gas inlet, a 2S0-mL dropping funnel, and a filtration tube attached to a 250-mL Schlenk flask (Fig. 1). The magnesium is suspended in S mL of thf to which 0.1 mL of 1,2-dibromoethane is added. 

Complex 2 decomposes rapidly in air, is only slightly soluble in thf, and is insoluble in many other inert organic solvents. The proton NMR spectrum (thf-dg) consists of a singlet at = 1.29 ppm (rel. to SiMe4.)(4H, C2H2) and multiplets at 5 = 6.48 and S = 6.08 ppm (center of each AA BB multiplet, 4H, CH). The X-ray structure of the magnesium-chloride-free macrocycle 2 has been determined.  

5 mL of 1.0 M HCl. The mixture is then shaken and the hexane layer separated and dried with anhydrous sodium carbonate. The solution is then filtered and concentrated using a rotary evaporator. The resulting pale yellow liquid boils at 60 to 62°C/0.1 torr. It is collected as 2.17 g of the colorless liquid, o-CgH4(CH2SiMe3)2, 71% based on the initial amount of o-bis(chloromethyl)benzene. (Checker reports yield of 1.5 g and boiling range 78-82 °C/0.1 torr.) 

Under an inert atmosphere butyllithium in hexane (purchased in bulk, 120 L, from Metallgesellsch t) (or may be purchased in smaller quantities from 

Aldrich)(25.5 mL, 1.6 M, 44 mmol) is added to a stirred ice-cooled solution of tmeda (6.6 mL, 44 mmol) and o-bis[(trimethylsilyl)methyl]benzene (5.0 g, 20 mmol) in a 50-mL Schlenk flask. The color of the solution changes from pale yellow to orange and, after allowing the solution to warm to ambient temperature, stirring is discontinued. The solution is then set aside for 12 h, during which time massive yellow crystals are deposited. Using a syringe, the supernatant liquid is removed, and the residual product washed three times with S-mL portions of hexane. It is then dried in vacuo at room temperature for 15 min. Yield 7.41 g (75%). 

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