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DOI: 10.1055/s-2007-984908
Stereoselective Alkylation of 7-Hydroxy-DHEA Derivatives
Publikationsverlauf
Publikationsdatum:
20. Juli 2007 (online)
Abstract
A series of 7-hydroxysteroids were stereoselectively alkylated with a variety of electron-rich nucleophiles to give 7-α-substituted steroids.
Key words
alkylations - steroids - Lewis acids - stereoselective - eliminations
- 1
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References and Notes
Nomenclature: 13a refers to the product 13 with the a nucleophile at the 7-position.
8The Multimax is a device used to monitor reactions by heat flow. This is accomplished by comparing the system’s jacket temperature (Tj) and the reaction temperature (Tr). Tr-Tj when plotted in real time gives a measure of the course of the reaction.
11Typical Experimental A solution of diacetate 1 (2.0 g, 5.15 mmol) and 2-methyl-furan (2.0 mL) in 20 mL of MeCN was equilibrated to 20 °C in the Mettler Multimax. Then Sc(OTf)3 (200 mg, 0.46 mmol) was added. The reaction was monitored by observing the Tr-Tj profile and by TLC (50% EtOAc-hexane). After complete reaction, H2O was added to the mixture and the product isolated with EtOAc. Crystallization from EtOAc-hexane afforded 1.71 g of product. The mother liquors were chromatographed on silica gel with 25% EtOAc-hexane to afford an additional 350 mg for a total of 97% yield.