Cascade Transformations in Organic Synthesis: I. The Interception of Carbene Alkyne Metathesis Intermediates II. Photo-Activation of Hydrazones III. Organocatalyzed Cascade Conjugate Addition/Aldol Annulation of Organoboronates

This dissertation describes cascade transformations in constructing complex building blocks in synthetic organic chemistry. It includes the interceptions of carbene alkyne metathesis intermediates, boron enolate intermediates, fused cyclopropene intermediates, and boronic acid intermediates. First, the multi-alkyne carbene cascade reaction under rhodium catalysis is discussed. Ten different diazoesters were synthesized and tested for cascade reactions. This transformation proved to be limited, since it only works for super engineered structures. It also reveals the possibility that carbene alkyne metathesis might be reversible. In the second chapter, a 1,5-triazole initiated carbene cascade reaction was discovered. A cyclopropene rearrangement mechanism converts those triazoles to spiro-1,3-enynes. Several different termination pathways were designed to achieve the formal 6-exo-dig and formal 7-endo-dig cyclization. Third, a light-promoted Barluenga-Valdés coupling was developed. Many different diarylalkanes and triarylboronates could be synthesized via this strategy. The mechanism of hydrazone decomposition via visible light was carefully elucidated. An organocatalyzed tandem conjugate addition/Aldol annulation of organoboronates was discussed in the last chapter. A variety of nucleophiles showed good compatibility with heterocycles. In addition, the strength of boron enolate intermediates were examined by intercepting with various electrophiles.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Houston

Year dc:date.issued

2025

Author dc:creator

• Dong, Zhencheng 1997-

Advisor dc:contributor.advisor

• May, Jeremy A.

Committee members dc:contributor.committeemember

• Daugulis, Olafs
• Scott, Gilbertson
• Statsyuk, Alexander V.
• Teets, Thomas

• Carbene Alkyne Metathesis
• Organoboronates
• Barluenga-Valés Coupling
• Cyclopropene Rearrangement
• C-H insertion
• Enantioselective Conjugate Addition
• Indanols
• Aldol Reaction
• Light Induced Hydrazone Decomposition

Language dc:language.iso

English

Handle dc:identifier.uri

https://hdl.handle.net/10657/20907

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/20907