反应详情

##STR20## The procedure of Example 1 was followed, with 6.75 g (25 mmol) of (+)-pinanediol benzylboronate, 27 mmol of dichloromethyllithium, 30 mL of tetrahydrofuran, 20 mL of diethyl ether, and 1.75 g (12.8 mmol) of anhydrous zinc chloride. NMR analysis indicated that the reaction was complete after 3.5 hr at 20°-25° C. When the petroleum ether extracts were concentrated, the residue crystallized and 7.9 g. (99%) was recovered. The recovered product was shown to be pure (+)-pinanediol (1S)-1-chloro-2-phenylethane-1-boronate by 200 MHz proton NMR analysis, with less than 0.5% of the (1R) isomer present. This was confirmed by comparison with an epimerized sample consisting of approximately equal amounts of the (1S) and (1R) isomers, which show distinctive peaks in the multiplet near δ 3.65 (especially the (1R) peaks at 718.6 Hz and 735.2 Hz and the (1S) peaks at 722.4 and 738.6 Hz downfield from tetramethylsilane). (For the preparation of this compound without the aid of zinc chloride catalysis, see Matteson et al., J. Am. Chem. Soc., Vol. 103, pp 52-5242 (1981).

1. concentrationWhen the petroleum ether extracts were concentrated
2. customthe residue crystallized
3. custom(99%) was recovered
4. custom(For the preparation of this compound without the aid of zinc chloride catalysis