Organocatalyzed C-C Ring Construction: The Jørgenson Synthesis of (+)-Estrone
Ana Maria Faísca Phillips and Maria Teresa Barros of the Universidade Nova de Lisboa added (Eur. J. Org. Chem. 2014, 152. ) the bromo ester 1 to cinnamaldehyde 2 to give the cyclopropyl phosphonate 3 in high ee. Mukund P. Sibi and Jayaraman Sivaguru of North Dakota State University used (Angew. Chem. Int. Ed. 2014, 53, 5604. ) an organocatalyst to mediate the 2+2 photocycloaddition of 4, leading to 5.
Shu-Li You of the Shanghai Institute of Organic Chemistry expanded (Org. Lett. 2014, 16, 1810. ) the four-membered ring of 6 to create the cyclopentanone 7 in high ee. Damien Bonne and Jean Rodriguez of Aix-Marseille Université condensed (Chem. Eur. J. 2014, 20, 410. ) the cyclopentanone 8 with 9 to give 10. Santanu Mukherjee of the Indian Institute of Science, Bangalore added (Chem. Sci. 2014, 5, 1627. ) the lactone 12 to the prochiral 11 to give 13 with remarkable diastereo- and enantiocontrol. Yixin Lu of the National University of Singapore constructed (Angew. Chem. Int. Ed. 2014, 53, 5643. ) the cyclopentene 16 by adding 14 to the allene 15.
Efraim Reyes and Luisa Carillo of the Universidad del País Vasco prepared (Chem. Eur. J. 2014, 20, 2145. ) the highly substituted cyclohexene 19 by combining 17 and 18. Maurizio Benaglia of the Università degli Studi di Milano added (Adv. Synth. Catal. 2014, 356, 493. ) the ketone 20 to 21 to create the cyclohexanone 22. Ben W. Greatrex of the University of New England in Australia used (J. Org. Chem. 2014, 79, 5088. ) an organocatalyst to cyclize the symmetrical dialdehyde 23 to the α-hydroxy ketone 24. Dieter Enders of RWTH Aachen added (Org. Lett. 2014, 16, 2954. ) the β-keto ester 25 to 26 to give an intermediate that was further condensed with 27 to complete the preparation of 28.
Eric N. Jacobsen of Harvard University prepared (Angew. Chem. Int. Ed. 2014, 53, 5912. ) the cycloheptenone 30 by the enantioselective intermolecular addition of the pyrilium salt derived from 29 to ethyl vinyl ether. Bor-Cherng Hong of the National Chung Cheng University initiated (Org. Lett. 2014, 16, 2724. ) the assembly of the steroid derivative 33 by the enantioselective addition of 32 to the unsaturated aldehyde 31.
Karl Anker Jørgenson of Aarhus University assembled (Angew. Chem. Int. Ed. 2014, 53, 4137. ) the tetracyclic steroid skeleton 36 by the addition of 34 to the cyclopentenone 35. Over several steps, 36 was carried on to (+)-Estrone (37).