Regioselective and Stereospecific Halosilylating Cleavage of the Oxirane System of Glycidol Derivatives as an Efficient Strategy to C2‐O‐Functionalized C3‐Vicinal Halohydrins

Abstract

Glycidyl esters and ethers undergo a regioselective and stereospecific opening of the oxirane ring upon treatment with trimethylsilyl halides (TMSX, X = Cl, Br, or I) in the presence of pyridine to produce the corresponding C2-O-trimethylsilyl-3(1)-halo-sn-glycerols in high yields. Trifluoroacetylation across the trimethylsilyloxy system of such C3-synthons with trifluoroacetic anhydride (TFAA) in the presence of a halide anion (e.g. Bu 4 NX; X = Cl, Br, or I), followed by removal of the trifluoroacetyl transient protection, pro-

Borinic Acid Catalyzed, Regioselective Chloroacylations and Chlorosulfonylations of 2,3-Epoxy Alcohols

“… , The syn configuration of 3a was established by X-ray crystallography. In comparison to methods for addition of “silyl–X” reagents across epoxides (e.g., halosilylations, azidosilylations, and cyanosilylations), additions of “acyl–X” are under-developed. The closest precedent for this type of reactivity is the organotin dichloride catalyzed chloroacylation of epoxides reported by Shibata and co-workers …”

An efficient catalytic three‐step synthesis of enantiopure triacylglycerols

“…Stamatov and Stawinski [16] presented a different strategy. Heating glycidyl ether 9 (Scheme 3I) with an excess of trifluoroacetic anhydride and Bu 4 NI afforded the iodohydrin, which after esterification in the same pot yielded 11 in 90%.…”

Preparation and characterization of magnetically separable MgFe2O4/Mg(OH)2 nanocomposite as an efficient heterogeneous catalyst for regioselective one‐pot synthesis of β‐chloroacetates from epoxides

“…Although ring‐opening of epoxides to β‐halohydrins has been extensively studied in recent years, the conversion of epoxides to β‐chloroesters has been rarely studied. Synthesis of β‐chloroesters from epoxides has been reported with TiCl 4 /EtOAc/imidazole, trimethylsilyl halides/pyridine/TFAA, t BuCH 2 COCl/BiCl 3 and acyl chlorides in combination with CrO 2 Cl 2 , CoCl 2 , Bu 2 SnCl 2 /Ph 3 P, hexaalkylguanidinium chloride, LiClO 4 , Zn, Bi (NO 3 ) 3 ⋅5H 2 O and TMSCl‐SnCl 2 . Some of these procedures suffer from disadvantages such as high temperatures, long reaction times, the use of harmful reagents, low efficiency and regioselectivity, formation of by‐products, incapability of catalyst recycling and the risk of metal remaining in the obtained product in pharmaceutical synthesis.…”