PREPARATION OF CHLOROETHYLBORONATE

PREPARATION OF CHLOROETHYLBORONATE

via Lithiation Carbon Insertion

Procedure

1. Cool solution of CH₂Cl₂/THF to -100 ^oC [1]

2. Add dropwise (by syringe) n-BuLi [2]

3. Stir at cold for 35 min ® pale yellow solu tion

4. Add dropwise (by syringe) SM/Et₂O [3] ® homogeneous solution

5. Quench w/ZnCl₂ (in Et₂O) at cold [4]

6. Warm to R.T. slowly and stir at R.T. for overnight

7. Concentrate on Rotovac (temp.:< 30 ^oC) ® yellow oil

8. Dilute residue w/ petroleum ether and sat. NH₄Cl

9. Extract aqueous layer w/ petroleum ether (2 times)

10. Filter combine organic layers thru bed of MgSO₄

11. Concentrate on Rotovac (temp.: <30 ^oC) ® crude as colorless oil

12. Distill by fractional vacuum

13. Collect product @ 70 - 75 ^oC/ 0.05 mmHg

14. NMR w/ CDCl₃. Yield 62% as colorless oil

Notes:

[1] Use liquid N₂ & 95% EtOH to make a slush. Cool THF to -10 ^oC before add CH₂Cl₂

[2] Run n-BuLi along the side of the cold flask to pre-cool. Inside temp: -100 ^oC during addition. ¯ white (LiCHCl₂)

[3] Inside temp: -100 ^oC during addition

[4] ZnCl₂ was fused under high vac until glassy form then make stock solution in dried Et₂O. ¯ white. Inside temp:

-100 ^oC during addition

JACS 108, pp 810-819 (1986). Organometallic 2, pp 1543-1545 (1983). J Organomet Chem 122, pp 145-149 (1976).

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