Triisopropyl phosphite → trans 4-(Bromomethyl)-2-(diisopropyloxyphosphinoyl)-1,3-dioxolane

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Reaction Conditions

Reaction Steps

To the mixture of cis and trans 4-(bromomethyl)-2-isopropoxy-1,3-dioxolane (example 2) (6.13 g, 9:1 of isopropoxy:methoxy) was added triisopropyl phosphite (4.43 mL, 18.0 mmol, 0.66 eq.), phosphorus trichloride (0.784 mL, 8.99 mmol, 0.33 eq.) and zinc chloride (few milligrams) at 0° C. The mixture was stirred at 0° C. for 2 hr and at room temperature for 10 hr. The crude mixture of cis and trans isomers in a 2:5 ratio was purified by flash chromatography on silica gel using dichloromethane:ethyl acetate 4:1 as eluant to give the cis isomer (0.242 g), a mixture of cis and trans isomers (3.13 g) and the trans isomer (3.15 g) for a total yield of 72%. Several chromatographic purifications were performed to obtain the cis and trans isomers in pure form.

Provenance & Evidence