Pd(PPh3)4/AgOAc-catalyzed coupling of 17-steroidal triflates and alkynes: Highly efficient synthesis of D-ring unsaturated 17-alkynylsteroids |
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Authors: | Qian Sun |
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Institution: | School of Chemistry and Chemical Engineering, Yangzhou University, Siwangting Road, Yangzhou 225002, Jiangsu, PR China |
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Abstract: | A novel and practical procedure was developed for the preparation of D-ring unsaturated 17-alkynyl steroids by Pd(PPh3)4/AgOAc-catalyzed coupling of steroidal 17-triflates and alkynes. Firstly treatment of the steroid-17-ones with PhN(Tf)2 and KHMDS in dried THF at −78 °C for 2 h gives the corresponding steroidal 17-triflates products in high yields (97-98%), following the coupling of steroidal 17-triflates and various 1-alkynes by Pd(PPh3)4/AgOAc-catalyzed in the presence of DIPEA for 24 h to yield the desired D-ring unsaturated 17-alkynyl steroids (86-97%). Moreover, it was found that the coupling reaction catalyzed by Pd(C6H5)3P]4/AgOAc system is selective for aryl triflates or vinyl triflates. By optimizing the reaction conditions, the sole C17-coupling products from steroidal bistriflates were obtained in satisfactory yields. Since D-ring unsaturated 17-alkynyl steroids with conjugated double and triplet bond can be subsequently converted into pentacyclic steroids and 17-oxosteroid derivatives at the side chain of D-ring, this general method provides a highly efficient route to these biologically important compounds. |
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Keywords: | Palladium catalyst Silver acetate 17-Ketosteroid Steroidal triflate 17-Alkynylsteroid |
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