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Cycloadditions and Annulation Methods Based on VinylketenesOur laboratory has pioneered the application of vinylketenes as four-carbon building blocks for the construction of four-, five-, six-, and eight-membered carbocyclic and heterocyclic compounds. In 1980 we reported the first synthesis of (trimethylsilyl) vinylketene, and in subsequent research we have developed several general methods for the preparation of (trialkylsilyl) vinylketenes ("TAS-vinylketenes"). We have shown that these remarkably stable ketenes are versatile, multi-functional synthetic building blocks which engage in a number of useful cycloaddition and annulation reactions leading to four-, five-, six-, and eight-membered carbocyclic and heterocyclic compounds.
Benzannulation Strategies for the Synthesis of Highly-Substituted Aromatic CompoundsReferences: "A Regiocontrolled Annulation Approach to Highly Substituted
Aromatic Compounds",
R. L. Danheiser and S. K. Gee, J.
Org. Chem. 1984, 49, 1672.
"Trialkylsiloxyalkynes: Synthesis and Aromatic Annulation Reactions", R.L. Danheiser, A. Nishida, S. Savariar, and M. P. Trova, Tetrahedron Lett. 1988, 29, 4917. "An Annulation Method for the Synthesis of Highly Substituted Polycyclic Aromatic and Heteroaromatic Compounds", R. L. Danheiser, R. G. Brisbois, J. J. Kowalczyk, and R.F. Miller, J. Am. Chem. Soc. 1990, 112, 3093. "The Reaction of (Trialkylsilyl)vinylketenes with Lithium Ynolates: A New Benzannulation Strategy", W. F. Austin, Y. Zhang, and R. L. Danheiser, Org. Lett. 2005, 7, 3905. "Synthesis of Polycyclic Benzofused Nitrogen Heterocycles via a Tandem Ynamide Benzannulation/Ring-Closing Metathesis Strategy. Application in a Formal Total Synthesis of (+)-FR900482", X. Y. Mak, A. L. Crombie, and R. L. Danheiser, J. Org. Chem. 2011, 76, 1852.
See also applications in the total synthesis of Mycophenolic acid, Maesanin, Dihydrotanshinone I, Tanishone I and IIA, Aegyptinones A and B, Salvilenone, Bergapten, Neocryptotanshinone, Cryptotanishone, Royleanone, and Ascochlorin.
Diels-Alder Reactions of TAS-VinylketenesReferences: "Trimethylsilylvinylketene: A Stable Vinylketene and Reactive Enophile in [4+2] cycloadditions", R. L. Danheiser and H. Sard, J. Org. Chem. 1980, 45, 4810. "(Trialkylsilyl)vinylketenes: Synthesis and Application as Diene Components in Diels-Alder Cycloadditions", J. L. Loebach, D. M. Bennett, and R. L. Danheiser, J. Org. Chem. 1998, 63, 8380. "Hetero [4+2] Cycloadditions of (Trialkylsilyl)vinylketenes. Synthesis of a,b-Unsaturated d-Valerolactones and -Lactams", D. M. Bennett, I. Okamoto, and R. L. Danheiser, Org. Lett. 1999, 1, 641.
[4+4] Annulation for the Synthesis of Eight-membered RingsReferences: "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.
[4+1] Annulation Route to Cyclopentenones and IndanonesReferences: "The Reaction of (Trialkylsilyl)vinylketenes with Carbenoid Reagents: A New [4+1] Annulation Route to Cyclopentenones", J. L. Loebach, D. M. Bennett and R. L. Danheiser, J. Am. Chem. Soc. 1998, 120, 9690. "Synthesis of 2-Indanones via [4 + 1] Annulation Reactions of (Trialkylsilyl)arylketenes", A. M. Dalton, Y. Zhang, C. P. Davie and R. L. Danheiser, Org. Lett. 2002, 4, 2465. "Stereoselective Synthesis of Highly Substituted Cyclopentenones through [4 + 1] Annulations of Trialkylsilyl Vinyl Ketenes with ±-Benzotriazolyl Organolithium Compounds", C. P. Davie and R. L. Danheiser, Angew. Chem. Int. Ed. 2005 , 44 , 5867.
Cyclohexenol Annulation StrategyReferences: "Cyclohexenol Annulation via the Alkoxy-accelerated Rearrangement of Vinylcyclobutanes", R. L. Danheiser, C. Martinez-Davila, and H. Sard, Tetrahedron 1981, 37, 3943.
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