Research in Organic Chemistry

Minehan Group

A Selection of Current Group Members.

From left: Vardan Papoian, Armen Tudjarian, John Alec Moral, Margaret Brown, Samuel Rodriguez-Torres

Not Pictured: Akop Yepramyan, Juan Sosa, Seong-Jin Moon, Jung Rim Suh, Bobby Salehani, Chikako Omura, Ben Sagot

Research in the Minehan group is primarily focused on the development of new synthetic methods for carbon-carbon bond-formation, with an emphasis on the use of environmentally friendly reagents and solvent systems. Inspiration for the development of these methods comes from the complex structures of naturally occurring substances of medicinal and pharmaceutical import. We are currently pursuing three main lines of investigation:

1. The [3,3]-sigmatropic rearrangement of aliphatic allyl-alkynyl ethers is a relatively unexplored reaction in organic synthesis. Allyl-alkynyl ethers could be generated from allyl-1,1-dichlorovinyl ethers by treatment with excess n-BuLi at low temperatures; However, subjecting allyl-dichlorovinyl ethers to these conditions, followed by quenching with an alcohol, leads to rearranged products in the form of gamma, delta-unsaturated esters. Sigmatropic rearrangement is occurring rapidly and stereospecifically at low temperatures in this process. Mechanistic investigations of this reaction are underway; the proposed ketene intermediate holds great synthetic promise, since it may be intercepted by a wide variety of nucleophiles to form an array of carbonyl compounds in a single step. We are also currently investigating alternative methods for preparing allyl-alkynyl ether intermediates that avoid the use of nucleophilic bases and toxic carbon tetrachloride.

2. Allylic substitution reactions are important and powerful methods for carbon-carbon bond-formation. Environmentally benign organoindium reagents participate in transition-metal catalyzed cross-coupling reactions and allylic substitution reactions. We have recently discovered that 1-acetoxy-2,7- and 2,8-enynes undergo a palladium-catalyzed cyclization / substitution reaction in the presence of organoindium reagents to form substituted 5- and 6-membered carbo- and heterocycles. We envision that this process may be extended to the stereoselective synthesis of diverse fused 6-5 and 6-6 ring systems. Since this process requires a stoichiometric amount of the triorganoindium reagent, we are currently developing a more atom-efficient cyclization/substitution process employing aryl(dimethoxy)indium reagents

3. Allylindium reagents, generated in-situ from allyl halides and indium metal, react with carbonyl compounds in water to form products containing a new carbon-carbon bond. We have prepared a series of silyl-substituted allylindium reagents that allow multiple carbon-carbon bonds to be formed in a single step in aqueous media upon reaction with appropriate electrophiles. Such reagents may be employed in an environmentally benign preparation of substituted pyrans and 7- and 8-membered carbocycles, which are at the core of a variety of biologically-important natural products.

Students in the Minehan group gain practical experience in the synthesis, purification, and spectroscopic characterization of organic molecules. Some examples of the useful skills obtained are:

1. Techniques for running reactions under inert atmosphere

2. Purification of compounds by column chromatography and radial chromatography

3. Analysis of reactions by thin-layer chromatography and GC-MS

4. Structure elucidation of synthetic compounds using NMR spectroscopy

Useful website for beginning laboratory students: Synthetic organic laboratory techniques

Research Funding

Henry Dreyfus Teacher Scholar Award

National Institutes of Health

American Chemical Society Petroleum Research Fund

Research Corporation

CSUN Competition for Research, Scholarship and Creative Activity Award

Selected Recent Publications: