Prof. Igor Alabugin, Florida State University

New radical and photochemical reactions of alkynes

In my talk, I will present a range of topics revolving around new reactions of alkynes. The processes are promoted by either photons or radicals and applied for preparation of interesting molecules and for inducing efficient light-activated DNA cleavage.

In the first part, I will discuss C1C5 cyclization of enediynes and analyze how this reaction can be controlled by communication of orthogonal orbitals originating from the crossing of out-of-plane and in-plane MOs in the vicinity of the transition state. I will illustrate how this chemistry can be combined with the proper recognition elements to achieve highly efficient double stranded (ds) DNA cleavage. I will also show how ds cleavage can be amplified at the acidic pH of cancer cells and how recognition of damaged DNA can be used for the conversion of single stranded DNA damage to the ds damage.

In the second part, I will discuss cascade radical cyclizations that utilize diaryl acetylenes in their triplet states as synthetic equivalents of 1,2-bicarbenes. Both chemical and photophysical factors such as the involvement of "phantom" excited states and the El-Sayed rules are important in directing reactivity.

In the final part, I will present the discovery of the first efficient 5-endo-dig radical cyclization of a carbon-centered radical - a process which remained unknown despite being predicted to be favorable by the Baldwin rules about 40 years ago.

For more information contact Prof. Uwe Bunz (404-385-1795).