Presentation Title

Efforts to Develop a Thiourea-Catalyzed Addition to ortho-Quinone Methides

Faculty Mentor

Raul Navarro Ph.D.

Start Date

17-11-2018 12:30 PM

End Date

17-11-2018 2:30 PM

Location

CREVELING 100

Session

POSTER 2

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

The synthesis of complex organic compounds relies upon alterations of simple, inexpensive aromatic structural motifs. Such alterations often require a thermodynamically strained dearomatization reaction. The scope of catalytic and enantioselective reactions that offer transformations of inexpensive aromatic derivatives remains rather limited because traditional methods often employ harsh and restricting conditions. We aim to attend to the narrow range of methodologies with the development of a catalytic asymmetric addition reaction to ortho-quinone methides (oQM) intermediates. We propose a dearomatization of β-halo substituted phenol derivatives caused by their subjection to the anion-binding capabilities of thiourea catalysts. The transiently formed oQM is anticipated to undergo nucleophilic attack to provide a broader scope of stereochemically rich aromatic building blocks. The successful development of in situ generated oQM reactions with an increased range of nucleophiles and substrates will allow greater efficiency in the construction of value-added intermediates.

We have optimized reaction conditions that afford the fundamental benzylic halide substrates, and we have begun to evaluate their ability to undergo a thiourea-catalyzed nucleophilic addition reaction. Our studies have produced an unexpected thiourea addition product which requires further characterization. Future work will focus on generating our desired reactivity with secondary halide substrates and various other thiourea catalysts.

Key Words: ortho-quinone methide, thiourea, dearomatization, nucleophilic addition

Summary of research results to be presented

We have successfully developed a robust platform to prepare a number of benzylic halide substrates beginning with 2-methoxybenzaldehyde. Though the resulting halide substrates are not chromatographically stable, the crude product proves to be clean enough for subsequent studies. Consequently, I have begun to evaluate their ability to undergo a thiourea-catalyzed dearomatization/addition sequence. Various trials and close analysis revealed an unexpected addition of the thiourea catalyst to our substrates, resulting in the formation of a peculiar thiourea adduct. Future studies will be aimed at further characterizing our unexpected thiourea addition product, and testing for similar reactivity between halo-substituted phenols and other thiourea compounds.

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Nov 17th, 12:30 PM Nov 17th, 2:30 PM

Efforts to Develop a Thiourea-Catalyzed Addition to ortho-Quinone Methides

CREVELING 100

The synthesis of complex organic compounds relies upon alterations of simple, inexpensive aromatic structural motifs. Such alterations often require a thermodynamically strained dearomatization reaction. The scope of catalytic and enantioselective reactions that offer transformations of inexpensive aromatic derivatives remains rather limited because traditional methods often employ harsh and restricting conditions. We aim to attend to the narrow range of methodologies with the development of a catalytic asymmetric addition reaction to ortho-quinone methides (oQM) intermediates. We propose a dearomatization of β-halo substituted phenol derivatives caused by their subjection to the anion-binding capabilities of thiourea catalysts. The transiently formed oQM is anticipated to undergo nucleophilic attack to provide a broader scope of stereochemically rich aromatic building blocks. The successful development of in situ generated oQM reactions with an increased range of nucleophiles and substrates will allow greater efficiency in the construction of value-added intermediates.

We have optimized reaction conditions that afford the fundamental benzylic halide substrates, and we have begun to evaluate their ability to undergo a thiourea-catalyzed nucleophilic addition reaction. Our studies have produced an unexpected thiourea addition product which requires further characterization. Future work will focus on generating our desired reactivity with secondary halide substrates and various other thiourea catalysts.

Key Words: ortho-quinone methide, thiourea, dearomatization, nucleophilic addition