Cascade Radical Cyclizations via Biradicals Generated from Enediynes, Enyne-Allenes, and Enyne-Ketenes

Abstract

IV. The Moore Cyclization of Enyne-Ketenes 216 A. Formation of o-Quinone Methides 218 B. The Spiro Structures and the Annelated Quinones 218 C. Biradicals versus Zwitterions 220 V. Conclusions 221 VI. Acknowledgements 221 VII. References and Notes 221 Kung K. Wang was born in Taiwan and received his B.S. degree from Tunghai University in 1972. After two years of compulsory military service, he joined the research group of Professor Herbert C. Brown at Purdue University and obtained his Ph.D. degree in 1979. He remained at Purdue for an additional two years before joining the faculty at West Virginia University. where he is now Professor of Chemistry. His research is in the area of designing and synthesizing multifunctional reagents substituted with combinations of boron, silicon, and tin appendages for synthetic applications.

Total Synthesis of the C‐1027 Chromophore Core: Extremely Facile Enediyne Formation through SmI2‐Mediated 1,2‐Elimination

“…The treatment of 14 with ethanol generated 16 (39 %), without the MPM protecting group, in addition to 15 (34 %). We believe the alcohol 16 to originate Communications 1778 www.angewandte.org from intramolecular 1,5-hydrogen abstraction by the phenyl radical at C3 in 17 to form the better stabilized benzylic radical 18, [16] followed by the addition of molecular oxygen and oxidative cleavage. [4] This pathway would contribute to the shorter half-life of 14 relative to that of 1, which has no proximal hydrogen atoms in a 1,5-relationship with C3 or C6.…”

Copper‐Catalyzed Synthesis of Tetrasubstituted Allenes from Quaternary Ammonium Salts and Grignard Reagents

“…Allenes are important units of natural products and biologically active compounds . Moreover, they are also useful building blocks in organic synthesis as demonstrated over the last few decades . Therefore, exploring simple and useful methods to synthesize various types of allenes is of great importance .…”

10.1007/s11176-008-2012-z

“…Bergman cyclization of carbocyclic 10-membered enediyne 11 and its nitrogen-and oxygen-containing analogs 12 and 13 [25] occurs at room temperature, whereas sulfur-containing compound 14 [16] Like Bergman cyclization leading to aromatic systems from enediynes, (Z)-hepta-1,2,4-trien-6-ynes 18 are capable of undergoing cyclization through a,3-didehydrotoluene diradicals (Myers3Saito cyclization). Unlike Bergman cyclization, acyclic enyne3 allenes 18321 react according to Myers3Saito under conditions similar to physiological (Scheme 5) [28,29].…”