Physical Sciences and Mathematics Commons^™

Generation And Reactions Of Cyclopropyl Vinylidene Carbenes, Nguyen Nhat Thu Le

Honors Theses

This study aimed to generate cyclopropyl methyl vinylidene carbene and cyclopropyl phenyl vinylidene carbene via photochemical routes. The precursors to these two carbenes were synthesized from phenanthrene by a two-step procedure. However, these precursors could not be fully purified because the second step generated many side products with similar properties as the precursors. A crude sample of each precursor were photolyzed with UV light in the range of 315 to 400 nm. Vinylidene carbenes are known to rapidly rearrange into alkynes, so the formation of these cyclopropyl vinylidene carbenes was monitored through the formation of their rearrangement products, cyclopropyl methyl …

Silicon And Tin Substituted Halocyclopropanes: Approaches To New Carbenes And Strained Cyclic Allenes, Noura Srour

Honors Theses

Chloro(trimethylsilyl)carbene and chloro(trimethylstannyl)carbene were generated through photolysis of cyclopropanated phenanthrene precursors which were synthesized in two steps. The photolysis reactions were done in the presence of cis and/or trans-beta-methylstyrene. Though product peaks corresponding to the carbene-alkene adducts were observed in the GCMS, the yields were too low for their isolation and complete characterization. Density functional theory (DFT) calculations were performed on the stereoisomers of the precursor to Chloro(trimethylsilyl)carbene and the carbene itself. Surprisingly, Chloro(trimethylsilyl)carbene’s triplet state was found to be more stable than the singlet at this level of theory.

In a related project, (1-bromo-1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)trimethylstannane, was …

Photochemical Generation Of Carbenes And Ketenes From Phenanthrene-Based Precursors Part I: Dimethylalkylidene Part Ii: Diphenylketene, Tarini S. Hardikar, Tarini Hardikar

Honors Theses

Previous studies have shown that the photolysis of phenanthrene-based cyclopropyl precursors can generate carbenes. In this work, a novel phenanthrene precursor was synthesized and photolyzed to generate the dimethylalkylidene carbene, which was subsequently trapped by cyclohexene. The car- bene was not prone to an internal rearrangement as some other carbenes are, and instead favored the intermolecular addition reaction. The precursor also underwent a rearrangement via pericyclic processes. A theoretical analysis of the potential energy surface of the system is presented using coupled cluster and density functional methods. Preliminary analysis for the precursor via time-resolved laser flash photolysis (LFP) was performed. …

Part I: Photochemical Generation Of Cyclohexyne From A Hydrocarbon Precursor Part Ii: A Triptycenyl Flower, Daniel Maurer

Honors Theses

Part I

Photolysis of phenanthrene-based methylenecyclopropane derivatives have previously been shown to generate alkylidenecarbenes, which readily rearrange to form alkynes. In this work, we show that photolysis of an analogous cyclic alkylidenecarbene precursor at ambi- ent temperature forms cyclohexyne via the putative cyclopentylidenecarbene, and can be trapped by dienes via a Diels-Alder reaction. Cyclohexyne and other strained cycloalkynes are of much interest to theoreticians and experimentalists alike. Results of coupled-cluster and DFT calculations on the potential energy surface of cyclopentylidenecarbene and the corresponding strained cyclohexyne are also presented. The photochemical generation of cy- clopentylidenecarbene, and thus cyclohexyne, from a hydrocarbon …

Phenanthrene...With A Twist!, Nicholas S. Kim

Honors Theses

The twisted and sterically hindered 4,5-dibromophenanthrene, was synthesized from 2,6-dibromoiodobenzene in a four-step pathway, or from 1,3-dibromobenzene in a three-step pathway. Then, 4,5-dibromophenanthrene was subjected to a Kumada coupling, leading to the synthesis of an even more twisted 4-bromo-5-tert-butylphenanthrene. Computational studies using density functional theory were performed to compare experimental and theoretical characteristics of these compounds, such as dihedral angles, optimized structures, and transition state energy barriers.

The purpose of these experiments is to fill gaps in chemical databases, synthesize more pronounced twists in normally planar phenanthrene molecules, and to ultimately synthesize 4,5-bis-tert-butylphenanthrene, which may have …

Experimental And Computational Study Of Methylphenylvinylidene And Its Rearrangements, Xi Yang

Honors Theses

In this study, the synthesis and properties were explored of the compound methylphenylvinylidene (MPV), a vinylidene carbene with methyl and phenyl groups as substituents. A phenanthrene-based precursor, 1-(1-phenylethylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, was synthesized in three steps and was subjected to photolysis in C₆D₆ at ambient temperature. During photolysis, the MPV carbene rearranged into 1-phenylpropyne via a 1,2-phenyl shift, instead of 1,2-methyl shift, confirmed by photolysis of ¹³C-labeled precursor. This experimental result is consistent with computational results using the CCSD(T)/cc-pVTZ//B3LYP/6-31+G* method. The calculations suggest that the 1,2-phenyl shift in singlet carbene requires 3.8 kcal/mol to overcome …

Generation Of 2-Adamantylidenecarbene From A Phenanthrene-Based Precursor, Christine E. Wamsley

Honors Theses

This thesis examines the generation of 2-adamantylidenecarbene from a phenanthrene-based precursor. A three-step synthetic procedure was used to generate the 2-adamantylidenecarbene precursor, which subsequently underwent photolysis to produce 2-adamantylidenecarbene. This product was trapped with cyclohexene. No evidence of a ring expansion to 4-homoadamantyne was observed. It was also noted that the target precursor underwent rearrangement during photolysis, leading to the formation of an isomer containing a seven-membered ring. This isomer did not photolyze. Additionally, computational studies were performed using Gaussian 09. Geometries were initially optimized and then, the single point energies of the singlet and triplet carbene states were calculated. …

Experimental And Computational Investigation Of Selected Β-Hydroxy Carbenes, Joseph D. Deangelo

Honors Theses

The photolytic precursor to the sterically hindered β-bis(tert)-butanol carbene, 3-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)-2,2,4,4-tetramethylpentan-3-ol was prepared in three steps from phenanthrene. Photolysis of the precursor generates the desired β-hydroxy carbene, an intermediate, which subsequently rearranges into two different observed products from an intramolecular C-H insertion and alkyl shift. Four intramolecular mechanisms were ultimately considered to account for the possible rearrangement pathways. Computational studies using density functional theory are also presented.

In addition, the photolytic precursors to two cyclic β-hydroxy carbenes, 1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclopropan-1-ol and 1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclobutan-1-ol, were also prepared through different synthetic routes from phenanthrene. …

Analysis Of The Electron Withdrawing Capability Of Acetylene Groups For Promoting Nucleophilic Aromatic Substitution, Eric D. Braunstein

Honors Theses

It is well known that electron withdrawing groups, such as nitro or carbonyl groups, activate benzene rings for nucleophilic aromatic substitution. However, little research has been done to investigate the electron withdrawing capability of acetylene groups for substitution of aromatic halides. Experimental and computational investigations on the reactivity of halogenated phenylacetylenes with oxygen and other nucleophiles will be described.

Using Azahetercyclic Electrophiles To Synthesize Novel Bicyclooxacalixarenes And Oxacalix[2]N-Hexylnaphthalimide[2]Naphthyridines, Doug Rooke

Honors Theses

Various bicyclooxacalixarenes, tricyclooxacalixarenes and oxacalix[2]N-hexylnapthalimide[2]naphthyridines are synthesized via SnAr condensation. This research has involved synthesis optimization. The oxacalix[2]N-hexylnaphthalimide[2]naphthyridines have exhibited host-guest binding in fluorescence experiments. These compounds have been characterized by NMR spectroscopy as well as single crystal X-ray diffraction.

Photochemical Generation And Intramolecular Chemistry Of Β-Alkoxycarbenes, Kimberly Graves

Honors Theses

The photolytic phenanthrene-based precursors for both β-methoxycarbene and β-ethoxycarbene were synthesized with and without a deuterium label attached to the a carbon. The incorporation of this deuterium label allowed distinction between a 1, 2-H shift and a 1, 2-O shift pathway to the respective alkyl vinyl ether, without the influence of a primary kinetic isotope effect. Photolyses of these precursors gave rearrangement products of the expected β-alkoxycarbenes. In the case of β-methoxycarbene, no methyl vinyl ether was observed due to its volatility. However, the appearance of aldehyde peaks in the NMR spectra, from an apparent further rearrangement to acetaldehyde through …