A very convenient route for the acylation of alcohols is provided by using a Bi(OTf)3 catalyst [Eq. (1)]. In this protocol hindered and functionalized alcohols are acylated at 25°C, and solvents can be employed without purification. R=primary, secondary, tertiary alkyl, aryl; R′=Me, Ph, tBu.
4
Both Sc(OTf)3 and Sc2O3, which is a starting material for the triflate, can be purchased from Aldrich. The price of Sc2O3 is $ 159.9 for 5 g (72.5 mmol). Bi2O3, the starting compound for Bi(OTf)3, is also commercially available, and its price is cheaper: $ 187.1 for 250 g (1.07 mol). Bi(OTf)3 is accessible alternatively by the reaction of Ph3Bi ($ 57.3, 25 g, 56.8 mmol) and TfOH. In this study, Bi(OTf)3 was prepared as a tetrahydrate according to this procedure. M. Labrouillere, C. Le Roux, H. Gaspard, A. Laporterie, J. Dubac, Tetrahedron Lett.1999, 40, 285, and references therein.
8
For the acetylation of the 12α-hydroxy group of methyl cholate, prolonged heating in Ac2O/pyridine or addition of an excess amount of 4-pyrrolidinopyridine is needed: G. Höfle, W. Steglich, Synthesis1971, 619.
Please check your email for instructions on resetting your password.
If you do not receive an email within 10 minutes, your email address may not be registered,
and you may need to create a new Wiley Online Library account.
Request Username
Can't sign in? Forgot your username?
Enter your email address below and we will send you your username
If the address matches an existing account you will receive an email with instructions to retrieve your username
The full text of this article hosted at iucr.org is unavailable due to technical difficulties.
39:16<>1.0.co;2-l.cover.gif)
