Igor Alabugin

Dr. Alabugin and his team have developed a method for preparing a cyclobutene compound or a cyclopentenone. The method comprises contacting an a,ß-diketone with a metal acetylide at a temperature below 0° C. to thereby form a reaction mixture comprising a bis-alkyne precursor. The bis-alkyne precursor rearranges into a bis-allenic intermediate, which undergoes further rearrangement into the cyclobutene compound or the cyclopentenone compound as the temperature of the reaction mixture increases from below 0° C. to above 0° C.

Several approaches to graphene nanoribbons exist in the literature. However, in all of them the central part of the molecule is built first and then additional rings are added at the periphery via electrophile induced cyclization or oxidative cyclodehydrogenation. These methods are difficult to apply to the preparation of non-symmetric graphene nanostructures.

Our approach utilizes a different class of starting materials and different chemistry for the formation of six-membered cycles. In our innovative approach, ortho polyyne chains of varying sizes, equipped with different functionalities, are built in a modular fashion using well-characterized and reliable cross-coupling chemistry. In the key step, these systems are then "zipped" up via an efficient cascade of fast and selective radical cyclizations. The selectivity of transformation is achieved via incorporation of a "weak link" - a chemically different functional group which can undergo transformation into a radical center in the presence of multiple alkynes.

Since modular assembly allows each of the peripheral groups to be unique, it will allow preparation of graphene substructures with custom shapes and functionalities.

Dr. Alabugin and his team have developed a traceless directing group in a radical cascade. The chemo- and regioselectivity of the initial attack in skipped oligoalkynes is controlled by a propargyl alkoxy moiety. Radical translocations lead to the boomerang return of radical center to the site of initial attack where it assists to the elimination of the directing functionality via ß-scission in the last step of the cascade. In some aspects, the reaction of the present invention is catalyzed by a stannane moiety, which allows further via facile reactions with electrophiles as well as Stille and Suzuki cross-coupling reactions. This selective radical transformation opens a new approach for the controlled transformation of skipped oligoalkynes into polycyclic ribbons of tunable dimensions.

A novel Rh(I)-catalyzed approach to synthesizing functionalized (E,Z) dienal compounds has been developed via tandem transformation where a stereoselective hydrogen transfer follows a propargyl Claisen rearrangement. Z-Stereochemistry of the first double bond suggests the involvement of a six-membered cyclic intermediate whereas the E-stereochemistry of the second double bond stems from the subsequent protodemetallation step giving an (E,Z)-dienal.

Dr. Alabugin and his team have designed a method is for the preparation of an aromatic carboxylic acid aryl ester or an N-aryl aromatic carboxamide. The method comprises contacting an O,O-diaryl thiocarbonate or an O-aryl-N-aryl thiocarbamate with a reactant that regioselectively reacts with sulfur, which contact causes an O-neophyl rearrangement, thereby forming either the aromatic carboxylic acid aryl ester or the N-aryl aromatic carboxamide, respectively.

Professor Alabugin's team has developped cycloalkynes with a twisted polyaromatic backbone to add axial chirality to the click chemistry toolbox. The “twisted and bent” cyclodecyne structural motif can be intertwined with dormant electronic effects to open a conceptually new way to control click reactivity. Although endocyclic heteroatoms can provide dual stabilization to the cycloalkyne via hyperconjugative (direct) and conjugative (remote) effects, these effects are weakened by the geometric constraints imposed by the twisted backbone. Structural reorganization in the transition state (TS) removes these constraints and unlocks the power of remote electronic effects for selective TS stabilization.

The chiral cyclodecynes can be prepared on gram scale in an enantiopure form and purified by recrystallization. Experimental kinetics confirm that these twisted cyclodecynes can be more reactive towards azides than activated cyclononynes and approach the reactivity of cyclooctynes.

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Pyrene and its derivatives are Polyaromatic Hydrocarbons (PAHs) that found uses in organic electronic devices such as OLEDs, OFETs, and OPVs due to their high fluorescence quantum yields and inherent deep-blue emission. New synthetic strategies are essential for selective functionalization of the pyrene core and modular control of its physical properties. In this work, we have developed a new strategy for the synthesis of unsymmetrical pyrenes and higher order PAHs via a one-pot double photocyclization sequence of simple and readily available starting materials. In the first part, we describe the development and optimization of this one-pot process to synthesize different unsymmetrical pyrenes containing functional groups of different donor and acceptor ability. The second part expands this new approach to the synthesis of higher order PAHs.

Key Words : LEDs, Chemical Synthesis, Flexible Displays

Current methods utilized to synthesize crowded polyaromatic architecture often use strategies that demand stringent design to achieve control over the size and substitution of the product. The proposed technique addresses this challenge by using a robust and flexible cyclization method in which a functional handle is installed during the reaction sequence to offer means for further extensions and functionalization.

The present invention is an efficient process to prepare synthetically challenging large distorted aromatics. The new approach developed at Florida State University efficiently transforms enynes into polyaromatic structures of precise dimensions and tunable electronic properties, solving the problem of selectivity in cascades aimed at the preparation of polyaromatic structures from conjugated enynes.

The overall process incorporates an unprecedented sequence in which chemo-and regioselective interaction of the triple bond with Bu₃Sn radicals originates from a conceptually novel source and propagates in such a way that renders alkenes synthetic equivalents of alkyns. By coupling the cyclization/rearrangement cascade with an aromatizing C-C bond fragmentation, the net result is a convenient transformation of readily available enyne reactants to a-Sn substituted naphthalenes that can serve as a lauching platform for the preparation of extended distorted polyaromatics.

The key challenge that had remained in the design of radical cascades was achieving control over chemoselectivity of initial radical attack and the subsequent cyclization mode. We resolved these problems by using the first radical enyne cascade in which chemo- and regioselective interaction of the triple bond with Bu₃Sn radicals originates from a novel 1,2 metallotropic shift.

The use of alkenes assists in the elimination of a radical leaving group via scission at the end of the cascade, aromatizing the final product without the need for external oxidants. This selective radical transformation opens a new approach for the controlled transformation of enynes into polycyclic distorted aromatics of tunable dimensions.

Advantages:

• The feasibility with which the scission of strong C-C bonds is accomplished under mild conditions.
• Provides a convenient and efficient method to synthesize large distorted aromatics and polycyclic ribbons of tunable dimensions.
• Installation of Bu₃Sn at a specific position and conversion of readily available enynes into highly valuable a-Sn naphthalene derivatives in high yields in a single cascade step