polyyne synthesis - toward new carbon allotropes:

Migrating Alkynes

We have recently shown that alkyne moieties readily undergo 1,2-shifts via an intermediate alkylidene carbene/carbenoid species. In these unprecedented reactions, lithium-halogen exchange between n-BuLi and 1,1-dibromo-2,2-diethynylethenes initiates alkyne migration via a Fritsch-Buttenberg-Wiechell (FBW) rearrangement and affords synthetically useful yields of a wide range of triynes and polyynes.[2] The dibromo-olefinic precursors are readily available, and they can be strategically functionalized in order to afford systems that are difficult or impossible to attain by other methods.[3-5] Examples include the series of linear polyynes and the two-dimensional arylyne building blocks. The ability to accomplish multiple FBW rearrangements within the same molecule promises to provide a synthetic route to a wide range of extended polyynes that are currently difficult or impossible to produce using known methods. We are currently expanding the scope of this new methodology to numerous new categories of unsaturated hydrocarbons including linear and cyclic polyyne systems as well as the formation of new allotropes of carbon such as cyclo-C18 and cyclo-C20.

Recent papers:

[1] "Polyyne Synthesis via Carbene/Carbenoid Rearrangements," W.A. Chalifoux, R.R. Tykwinski, Chem. Rec.2006, 6, 169-182.

[2] "A One-pot Synthesis and Functionalization of Polyynes," Y. Morisaki, T. Luu, R.R. Tykwinski, Org. Lett. 2006, 8, 689-692.

[3]"Regioselective Trapping of Terminal Polyynes with Benzyl Azide," T. Luu, R. McDonald, R.R. Tykwinski, Org. Lett. 2006, 8, 6035-6038.

[4] "Polyynes as a Model for Carbyne: Synthesis, Physical Properties and Nonlinear Optical Response," S. Eisler, A.D. Slepkov, E. Elliott, T. Luu, R. McDonald, F.A. Hegmann, R.R. Tykwinski, J. Am. Chem. Soc. 2005, 127, 2666-2676.

[5] "A Divergent Synthesis of Triyne Natural Products and Glycosylated Analogues Using a Carbenoid Rearrangement," T. Luu, W. Shi, T.L. Lowary, R.R. Tykwinski, Synthesis 2005, 3167-3178 (invited feature article).

[6] "Synthesis, Structure and Nonlinear Optical Properties of Diarylpolyynes," T. Luu, E. Elliott, A.D. Slepkov, S. Eisler, R. McDonald, F.A. Hegmann, R.R. Tykwinski, Org. Lett. 2005, 7, 51-54.

[7] "The Surprising Nonlinear Optical Properties of Conjugated Polyynes,” A.D. Slepkov, S. Eisler, E. Elliott, F.A. Hegmann, R.R. Tykwinski, J. Chem. Phys. 2004, 120, 6807–6810.

[8] Alkyne Migration in Vinylidene Carbenoid Species: A New Method of Polyyne Synthesis." S. Eisler, N. Cahal, R. McDonald, and R. R. Tykwinski, Chem. Eur. J. 2003, 9, 2542-2550.

[9] "Synthesis of Unsymmetrical Substituted 1,3-Butadiynes and 1,3,5-Hexatriynes via Alkylidene Carbenoid Rearrangements," L.K. Shi Shun, E.T. Chernick, S. Eisler, R.R. Tykwinski, J. Org. Chem. 2003, 68, 1339-1347.

[10] "Migrating Alkynes in Vinylidene Carbenoids: An Unprecedented Route to Polyynes," S. Eisler, R.R. Tykwinski, J. Am. Chem. Soc. 2000, 122, 10736-10737.

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