Event Title

The Reaction of O-Silylated Cyanohydrin Anions with Epoxides as an Alternative for the Enantio- and Diastereoselective Preparation of Aldols

Poster Number

059

Presenter Information

Caylie McGlade, Winthrop University

Faculty Mentor

Aaron Hartel, Ph.D.

College

College of Arts and Sciences

Department

Chemistry, Physics, and Geology

Location

Richardson Ballroom

Start Date

20-4-2018 2:15 PM

End Date

20-4-2018 4:15 PM

Description

One of the most important carbon-carbon bond-forming reactions in organic chemistry is the aldol condensation, which forms a beta-hydroxy carbonyl, or “aldol” product. With this type of reaction, up to two new chiral centers can form, making diastereoselectivity important; however, it is difficult to achieve with the traditional aldol reaction, requiring the use of expensive chiral auxiliaries and additional synthetic steps. Other advancements have been made to produce an aldol product through non-aldol pathways, such as the Jung reaction, which uses the rearrangement of a functionalized epoxide and provides good diastereoselectivity but does not form a carbon-carbon bond. Our chemistry uses an O-silylated cyanohydrin anion reacted with an epoxide to form the aldol product, which results in good diastereoselectivity while forming a carbon-carbon bond. Previous research has gone into optimizing reaction conditions and finding compatible epoxides, while this summer we focused on the scope of which aryl groups on the cyanohydrin worked with the reaction. A series of O-silylated cyanohydrins were synthesized and reacted with LiHMDS base to deprotonate, then reacted with an epoxide in the alkylation step. The reaction was stopped with a subsurface quench in saturated aqueous ammonium chloride. The product was then reacted with TBAF to deprotect the cyanohydrin. Thus far, the only aryl group substitutions to work with the reaction are naphthyl, phenyl, and pyridine groups. Further exploration of the scope of this project will include synthesis and reaction of other groups on the cyanohydrin.

Previously Presented/Performed?

Southeast Regional Meeting of the American Chemical Society (SERMACS), Charlotte, North Carolina, November 2017; South Carolina EPSCoR/IDeA State Conference, Columbia, South Carolina, April 2018

Grant Support?

Supported by an SC INBRE grant from the National Institute of General Medical Sciences (NIH-NIGMS), and by an REU grant from the South Carolina EPSCoR/IDeA Program

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Apr 20th, 2:15 PM Apr 20th, 4:15 PM

The Reaction of O-Silylated Cyanohydrin Anions with Epoxides as an Alternative for the Enantio- and Diastereoselective Preparation of Aldols

Richardson Ballroom

One of the most important carbon-carbon bond-forming reactions in organic chemistry is the aldol condensation, which forms a beta-hydroxy carbonyl, or “aldol” product. With this type of reaction, up to two new chiral centers can form, making diastereoselectivity important; however, it is difficult to achieve with the traditional aldol reaction, requiring the use of expensive chiral auxiliaries and additional synthetic steps. Other advancements have been made to produce an aldol product through non-aldol pathways, such as the Jung reaction, which uses the rearrangement of a functionalized epoxide and provides good diastereoselectivity but does not form a carbon-carbon bond. Our chemistry uses an O-silylated cyanohydrin anion reacted with an epoxide to form the aldol product, which results in good diastereoselectivity while forming a carbon-carbon bond. Previous research has gone into optimizing reaction conditions and finding compatible epoxides, while this summer we focused on the scope of which aryl groups on the cyanohydrin worked with the reaction. A series of O-silylated cyanohydrins were synthesized and reacted with LiHMDS base to deprotonate, then reacted with an epoxide in the alkylation step. The reaction was stopped with a subsurface quench in saturated aqueous ammonium chloride. The product was then reacted with TBAF to deprotect the cyanohydrin. Thus far, the only aryl group substitutions to work with the reaction are naphthyl, phenyl, and pyridine groups. Further exploration of the scope of this project will include synthesis and reaction of other groups on the cyanohydrin.