Making new C-C and C-H bonds in cascade transformations of alkynes 

We take advantage of the synthetic opportunities offered by the simultaneous presence of two reactive p-bonds of the alkyne moiety for the design of new cascade transformations of alkynes. In these reactions, one can form up to four new C-C bonds, both single and double, and/or couple the C-C bond formation with the C-H bond formation. In the exteme cases, one can move the cascade even further and break all three bonds between the two alkyne carbons, creating six new bonds!

Mixing C-H and C-C bonds formation from alkynes:
new chemistry for efficient DNA-photocleavage 

We have redirected a well-known  reaction of bis-alkynes, aka enediynes, (the Bergman cyclization) into a new path (C1-C5 cyclization). In the new enediyne-indene transformation, the C-C bond formation is coupled with C-H bond formation, leading to two hydrogen transfers to each of the triple bonds. The overall transfer of four hydrogen atoms suggested us that the family of compounds would be more efficient in accomplishing double-strand DNA cleavage than traditional enediynes which are capable fo only two H-atom abstractions. Check for details here!

Building carbon nanostructures from scratch?

We found a remarkable reaction which transform a tris-alkyne into a larger polycyclic structure via a radical five-step cascade (with ~93% yield per step). DFT calculations predict the key reactions in this sequence (5-exo-dig and 6-exo-dig cyclizations) to have very low barriers. Encouraged by these results, we are redesigning this cascade transformation towards preparation of larger carbon-nanostructures related to graphene nanoribbons and tips of carbon nanotubes.

The parachute reaction: alkynes as synthetic equivalents of 1,2-bicarbenes

In a very interesting photochemical "cycloaddition", alkyne form four new C-C bonds and two contiguous stereocenters. From a topological perspective, alkyne behave in this reaction as synthetic equivalents of 1,2-bicarbenes. However, the mechanism is more complex and interesting. We suggested that it involves a "boomerang" radical addition/cyclization sequence (read more..) and used this reaction for the preparation of an interesitng family of porous hybrid organic/inorganic materials (read more..).

There are indications that this reaction will help us to understand the mechanism of photochemical DNA-modification by alkynes.

We are also working on expanding the scope of this process and develop it into a photochemical analog of "click chemistry".