Lead tetra-acetate-hydrogen fluoride

The replacement of OH by F in aliphatic alcohols has been extended to sterols.24 The trimethylsilyl ether (62) of pregnenolone on treatment with PhPF4 in methylene chloride produced as the sole isolated product (70%) the A5-3/3-fluoride (63). Pregnenolone acetate (64) reacted with a lead tetra-acetate-hydrogen fluoride mixture [Pb(OAc)4-12HF] in methylene chloride at — 50 °C to yield the 5a,6a-difluoride (65) (20%) and a product (66) of rearrangement (70%).25... 

Rearrangement during solvolysis of the tosylate ofa 4-hydroxymethyl-4-methyl-3-oxo-steroid is discussed on p. 276. Simultaneous contraction and expansion of adjoining rings affords some curious products when cholesterol reacts with lead tetra-acetate and hydrogen fluoride (p. 258). The 12 ff-hydroxyconanine mesylate... 

With norbornene in moist dimethyl sulphoxide, NBS gives a number of products earlier product studies are shown to be incorrect. The results (Scheme 4) make an interesting comparison with addition of iodine monochloride, lead tetra-acetate and lead tetra-acetate in the presence of hydrogen fluoride, and thallium trinitrate.Also shown in Scheme 4 are products of bromination and chlorination of norbornene. ... 

Glycosyl fluorides have also been prepared by treatment of per-O-acyl or partially 0-acylated sugars with hydrogen fluoride [liquid HF (for example, see Refs. 38 and 39) or HF in acetic acid or dichloromethane], as exemplified by 2,3,4-tri-O-benzyl-a-D-xylopyranosyl (18), a-D-glucopyranosyl (19), tetra-O-pivaloyl-a-D-glucopyranosyl (20), and 2,3,5-tri-O-acetyl-D-xylofur-anosyl fluorides (21) (see Table 1). Frequently, HF treatment - leads to... 

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