Synthesis of Four-Membered Rings via Ketene [2+2] Cycloadditions
The development of new methods for the generation of ketenes has been a long-standing concern in our laboratory. Our recent discovery of a new method for the synthesis of thio-substituted ketenes was highlighted on the cover of the Journal of Organic Chemistry.
This chemistry has been applied in efficient synthetic routes to cyclobutanones, cyclobutenones, and b-lactams.
"The Regiochemical Course of [2 + 2] Cycloadditions of Dichloroketene with Vinyl- and Alkynylsilanes", R. L. Danheiser and H. Sard, Tetrahedron Lett. 1983, 24, 23.
"A General Method for the Reductive Dechlorination of 4,4-Dichlorocyclobutenones", R. L. Danheiser and S. Savariar, Tetrahedron Lett. 1987, 28, 3299.
"3-Butylcyclobutenone", R. L. Danheiser, S. Savariar, and D. D. Cha, Organic Syntheses 1989, 68, 32.
"Rhodium-Catalyzed Rearrangement of a-Diazo Thiol Esters to Thio-substituted Ketenes. Application in the Synthesis of Cyclobutanones, Cyclobutenones, and b-Lactams", M. D. Lawlor, T. W. Lee, and R. L. Danheiser, J. Org. Chem. 2000, 65, 4375.
"Generation and [2 + 2] Cycloadditions of Thio-Substituted Ketenes: trans-1-(4-Methoxyphenyl)-4-phenyl-3-(phenylthio)azetidin-2-one", R. L. Danheiser, I. Okamoto, M. D. Lawlor, and T. W. Lee, Organic Syntheses, 2003, 80, 160.
"[2 + 2] Cycloaddition of Ketenes with Ynamides. A General Method for the Synthesis of 3-Aminocyclobutenone Derivatives", A. L. Kohnen, X. Y. Mak, T. Y. Lam, J. R. Dunetz, and R. L. Danheiser, Tetrahedron 2006, 62, 3815.
"A New Route to Silyl-Substituted Cyclobutenones and Silyliketenes", K. Benda, T. Knoth, R. L. Danheiser, and E. Schaumann, Tetrahedron Lett. 2011, 52, 46.
"Synthesis of 2-Iodoynamides and Regioselective [2 + 2] Cycloadditions with Ketene", Y.-P. Wang and R. L. Danheiser, Tetrahedron Lett. 2011, 52, 2111.
Applications in Annulation Strategies
"Cyclohexenol Annulation via the Alkoxy-accelerated Rearrangement of Vinylcyclobutanes", R. L. Danheiser, C. Martinez-Davila, and H. Sard, Tetrahedron 1981, 37, 3943.
"A [4+4] Annulation Approach to Eight-Membered Carbocyclic Compounds", R. L. Danheiser, S. K. Gee, and H. Sard, J. Am. Chem. Soc. 1982, 104, 7670.