1-Aza-2-azoniaallene salts, derived by oxidation of substituted hydrazones, are highly reactive cationic heteroallenes. These species participate in several mechanistically distinct reactions including: (1) intramolecular [3+2] cycloadditions, (2) polar [4 +2] cycloadditions, (3) stereospecific C-H aminations, (4) electrophilic aromatic substitutions, and (5) chloroamination reactions. We have shown that this versatile reactivity is governed by the length of the tether and nature of the π-system.
A novel intramolecular electrophilic aromatic substitution reaction is observed when the tether length separating the 1-aza-2-azoniaallene salt and a pendant aryl ring is three methylene units to generate alkylaryl azo products. Variations in the electronics and sterics of the heteroallenes greatly affects their reactivity. The azo product obtained from 5-phenyl-pentan-2-one undergoes spontaneous photochemical cleavage, exhibiting interesting applications to this class of compounds.
Heteroallenes derived from pent-5-ene-2-one scaffolds undergo a concerted polar [4+2] cycloaddition to give a 1,2,3,4-tetrahydrocinnoline product. These products are structural motifs found in biologically and pharmaceutically active compounds. This reaction can give the structurally complex tetracyclic iminium salt from a cyclohexene based heteroallene which serves as good precedence to the key step of our proposed synthesis of a terpene indole alkaloid, (+)-ibophyllidine.
Identifer | oai:union.ndltd.org:uvm.edu/oai:scholarworks.uvm.edu:graddis-1954 |
Date | 01 January 2018 |
Creators | Srinivasan, Ramya |
Publisher | ScholarWorks @ UVM |
Source Sets | University of Vermont |
Language | English |
Detected Language | English |
Type | text |
Format | application/pdf |
Source | Graduate College Dissertations and Theses |
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