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Researchers have previously attempted to produce yields of c-enhanced diphenylcyclohexadienylidene through the utilization of acetic-1-C acid as the synthetic precursor and converting this acid to an acid chloride. These attempts produced little or no yields of the c-enhanced dienylidene. However, later studies allowed researchers to develop a single mechanism to produce the desired yields. This mechanism utilized pyrolytic decomposition of the Li salt and the formation of an isobenzene species to be followed by subsequent phenyl and hydrogen migrations.

Computational results suggest that the barrier to the concerted ring opening of silacyclopropene to vinylsilylene is lower than the barrier to forming silylacetylene. The deltaZPE-corrected barriers derived by (12,12)CASPT2 calculations are 32.2 and 38.7 kcal/mol, respectively, while the corresponding values derived by B3LYP calculations are 35.8 and 42.2 kcal/mol. The barrier to ring closure of vinylsilylene to silacyclopropene is found to be 31.5 kcal/mol by (12,12)CASPT2 and 31.7 kcal/mol by B3LYP.

Research was conducted to examine the spectral and chemical characteristics of 3,4-benzotropone which reveal substantial electronic polarization in its ground state through a significant contribution of polar resonance form to the molecule. The spectroscopic experiment demonstrates that 3,4-benzotropone is significantly polarized in the ground state. Mechanistic investigation indicate that the rearrangements might sterically be impeded in the constraining rigid glassy medium.

Research was conducted to examine the asymmetric synthesis of diverse novel pirocyclic cyclohexonenes that include those bearing additional functionality. Results demonstrate that the sequential thio-Claisen rearrangement can be used to introduce two different allylic moieties in a diastereoselective fashion. Findings also show that the presence of functionality on the allylic bromide permits the rearrangement to proceed with a high degree of stereoselectivity.

Research was conducted to examine the suprafacial and antarafacial paths for the thermal vinylcyclopropane-to-cyclopentene rearrangement of 1-ethenylbicyclo(4.1.0)heptane to bicyclo(4.3.0)non-1(9)-ene. Both exo and endo isomers of 8-d-bicyclo-(4.3.0)non-1(9)-ene were formed in the analogous rearrangement of 1-(2'-(E)-d-ethenyl)bicyclo(4.1.0)heptane which occurred with the allylic moiety being employed in both suprafacial and antarafacial stereochemical ways.

A study on the preparation of ordered-assembly molecular materials using metal-ligand bonds describes the synthesis, characterization and solid-state structure of the M4E6 complexes where M = Fe, Ga. A major objective of the experiment was to scrutinize the mechanical coupling between the vertices of a tetrahedral cluster using variable temperature nuclear magnetic resonance studies. Experimental methodology, results and conclusions are discussed.

Angle strain influences preference for a singlet ground state in small-ring vinylcarbenes, in contrast to the parent vinylcarbene. As the angle at the carbenic center is permitted to widen with expanding ring size, the triplet becomes the ground state. The six-membered ring for which singlet and triplet states are close in energy provides the break-even point. For five-membered and larger rings, the singlet states are expected to immediately isomerize to the corresponding olefins by a 1,2 H migration of the neighboring methylenic hydrogen. These were gleaned from the computational study of the singlet and triplet states of four carbenes and some of their isomers to assess the effect of angle strain on the S-T gap of cyclic alkenylidenes.

The remote Pummerer-type reaction of the mono-sulfoxide of p-bis(methylthio)-aromatic proceeds via an intermolecular through-space interaction between the sulfonium and the sulfenyl sulfur atoms. This is better than an intramolecular through-bond interaction and the abstraction of an alpha-proton of the sulfonium group leading to the Pummerer product. and sulfenyl sulfur atoms. A dithia dication dimer and/or a bis(dithia dication) cyclic dimer are proposed as intermediates.

Research was conducted to examine the thermal rearrangement of ethynylarenes to cyclopentafused polycyclic aromatic hydrocarbons using GLYP/6-311G electronic structure calculations. Five distinct mechanisms are potentially possible for the thermal rearrangement of ethynylarenes to cyclopentafused polycyclic aromatic hydrocarbons. Out of the five, only a one-step process that involved hydrogen migration immediately followed by ring closure is clearly favored due to a substantially lower energy barrier.

Research was conducted to examine the thermolysis of 5-azidopyrazoles which yields highly substituted furans and pyrazoles. The reaction apparently involved a disproportionation-like transfer of redox equivalents from one reaction pathway to another which coupled the formation of the two products. Results suggest that producing two different heterocycles from the same starting material is possible under effectively the same conditions by adding either a reducing or an oxidizing agent.

Research was conducted to examine the rearrangement of a monomeric Pt complex that leads to C-S bond cleavage and formation of an unusual dimer having both thioether and thiolate donors. The dimer was observed to have the ability to be assembled from its constituent parts. Results suggest that the arrangement of the constituents about the Pt atoms in the dimer is an energetically favorable one.

The laser flash photolysis of methyl 2-diazo(2-naphthyl)acetate at room temperature and at 77 K has been studied. The process produces singlet 2-naphthyl(carbomethoxy)carbene. It takes only 350 ps to 1 ns for the singlet carbene to relax to its lower energy triplet state. The singlet to triplet carbene intersystem crossing occurs faster than the Wolff rearrangement to the corresponding ketene. It has been observed that the carbene produces the ketene and its formation is not dependent on the excited state of the diazo compound.

Time-resolved infrared spectroscopy was used in studying methyl 2-diazo-(2-naphthyl) acetate and 2-naphthyl(carbomethoxy)carbene to determine the role of diazocarbonyl excited states in Wolff rearrangement chemistry. Results indicate that the diazo excited state has very little contribution in the ketene product of the rearrangement after laser excitation of the diazoester.

The photoisomerization of the 4-peroxy-2-enones via singlet oxygenation and peroxy radical rearrangement was applied to the total synthesis of the alkoxydioxine natural products chondrillin and plakorin. Analysis of the optical rotation of the synthetic material indicated that both chondrillin and plakorin are either enantiomerically pure or highly enriched in one enantiomer. Results also showed that the configuration of chondrillin in past literature is erroneous.

Research was conducted to examine the total synthesis of spirotryprostatin A using the oxidative rearrangement of the beta-carboline derivative to an oxindole via the action of N-bromosuccinimide as a major step in the process. This was followed by the introduction of a diketopiperazine. Results demonstrate that the same process using a methoxytryptophan derivative produced the parent structures.

Research was conducted to examine the synthesis of unit A of the cryptophycins from (s)-trans-3-penten-2-ol and from (s)-trans-4-hexen-3-ol using a (2,3)-Wittig rearrangement of a propargyl ether as the key stereodetermining step. The investigation involved the elaboration of the rearrangement product, selective ozonolytic cleavage and Wittig olefination. Results indicate that the introduction of the phenyl group at the end of the sequence provides a convenient access to cryptophycin analogues.

Research was conducted to examine the involvement of 3-hydroxylaminophenol mutase from Ralstonia eutropha JMP134 in the degradative pathway of 3-nitrophenol. The 3HAP mutase was purified and characterized to gain an insight into the reaction mechanism and to find out if the enzymatic isomerization of 3-hydroxylaminophenol to aminohydroquinone in R. eutropha JMP134 was catalyzed by a single enzyme. Results indicate an enzymatic mechanism that is comparable to that of acid-catalyzed Bamberger rearrangement.

The composite S2 to S1 to S0 relaxation/reaction paths which describe the photoarrangement of the highly alkylated diene 2,3-di-tert-butylbuta-1,3-diene and of the corresponding parent compound s-cis-buta-1,3-diene were investigated. The potential energy surfaces were calculated by high-level ab initio chemical methods (MC-SCF and multireference Moller-Plesset perturbation theory). The results showed that the role of the bulky substituents in prompting the production of the highly strained bicyclobutane was to drive the relaxation process along the path which is structurally different from that of the unsubstituted diene.

A study was conducted to analyze the coenzyme-B12-dependent rearrangement of 2-methyleneglutarate to (R)-3-methylitaconate catalyzed by 2-methyleneglutarate mutase. Ab initio molecular orbital theory was utilized to carry out the analysis. A transient fragmentation of the substrate after recombination of the fragments was examined. Results indicated that a cyclization/ring-opening mechanism needed less energy than the fragmentation and recombination mechanism.

1,2-oxazine and various furan derivatives have been synthesized via photochemical vinylcyclopropane rearrangements of 1-substituted-3-(2,2-diphenylvinyl)-2,2-dimethylcyclopropanes to cyclopentenes and different heterocycles. Significant differences in reactivity between the triplet-sensitized and the direct irradiations have been observed for the first time. Substitution had a marked influence at the 1-position on the photochemical reactivity of 1-substituted-2-vinylcyclopropanes.

Research was conducted to examine a novel and short synthetic method for the stereoselective synthesis of 1,3-diols. The method was developed using an unusual reductive rearrangement of a series of alpha-hydroxy epoxides with aluminum isopropoxide. The process was also examined using deuterium-labeled aluminum isopropoxide. Results indicate that the reductive rearrangement method is an effective approach for the stereoselective synthesis of 1,3-diols and reveals a versatile and practical asymmetric organic reaction.

Experiments were performed to investigate the Cope rearrangement in 1,2,6 heptatriene (1) to 3-methylene-1,5,hexadiene (3). CASPT2 and UB3LYP calculations describing the potential energy surface for the Cope rearrangement of 1 to 3 were performed. Two different pathways which converged on a common transition state were identified. The pathways on the potential energy surface led to the formation of a diradical intermediate or directly to the product which explain the conclusions in several oxygen-trapping experiments.

The rearrangement of substituted allyl benzyl ethers induced by zeolite beta to yield 4-arylbutanals was investigated with respect to the substituents in the aromatic ring. The analysis of substrates carrying other aromatic parts than p-methoxyphenyl was conducted as part of the study of the scope and limitations of the BenzAll rearrangement. It was found that the resulting aldehydes undergo spontaneous cyclization to produce dihydronaphthalene derivatives in some cases.

The rearrangement of camphene hydrochloride to isobornyl chloride was investigated using density functional theory calculations. To this end, computed and experimental carbon-13 and methyl proton chemical shifts were compared to identify uncertainties in configurations of camphene hydrochloride and isobornyl chloride. Experimental results revealed second-order kinetics, high stereoselectivity and low enthalpy of activation associated with camphene hydrochloride rearrangement.

Research was conducted to examine the reaction mechanism of the Boulton-Katritzky rearrangement using detailed ab initio and density functional methods. Two different reaction paths for the 4-nitrobenzofuroxan rearrangement were analyzed at the RHF, MP2, MP4(SDQ), B3-LYP and BH&H-LYP levels with more energy refinements using coupled-cluster theory. Results indicate the absence of a tricyclic intermediate.

Research was conducted to attempt the preparation of various substituted cyclobutylmethyl cations and the preparation as well as the characterization of the persistent cyclobutyldicyclopropylmethylium cation. Variable-temperature NMR studies of the cation was also performed. Results indicate that primary and secondary cyclobutylmethyl cations were elusive in superacidic media even at low temperatures. It was also found that cyclobutylmethyl cations readily undergo ring expansion-rearrangement to yield the corresponding cyclopentyl cations.

A study was conducted to analyze the solvolyses of caryophyllen-8-beta-yl p-nitrobenzoate and 15-norcaryophyllen-8-beta-yl tosylate (15-OT) as possible model reactions for the biogenesis of the tricyclic presilphiperfolanol sesquiterpenes. Two kinds of mechanisms for the conversion of 15-OTs to 12-nor-8-alpha-presilphiperfolan-9-beta-ol were determined by 1,2-migration of cyclobutane ring bonds. The first conversion of a caryophyllene derivative supporting a 4,5-double bond was achieved.

A study was conducted to analyze a novel way to several-membered ring N,S-heterocycles supporting sulfoxide electrophilic sulfenylation followed by ring expansion of the determined sulfonium salt intermediate for 9 and 10-membered-ring compounds. The analysis was carried out under Pummerer rearrangement conditions. Results indicated that the annelation approach is capable of supporting a range of new compounds from a number of synthetic protocols.

Allene oxide rearranges to cyclopropanone in a stepwise manner, wherein allene oxide undergoes conversion to oxyallyl through a new transition structure, which, in turn, undergoes ring closure to cyclopropanone. This was gleaned from a theoretical study of the rearrangement of allene oxide to cyclopropanone and the racemization and isomerization of substituted cyclopropanones. Oxyallyl was also an intermediate in both the racemization and isomerization reactions of substituted cyclopropanones. Two oxyallyls are linked via a 'perpendicular' oxyallyl transition structure, explaining the isomerization reactions of substituted cyclopropanones.

Tandem Claisen rearrangement was found to be effective in synthesizing bis-calix(n)arenes, both singly and doubly bridged on the lower rims, to afford compounds for complexation studies of fullerenes. An examination of the complexation behavior of bis-calix(n)arenes that are singly and doubly bridged at the upper rims with 2-butenyl or 2-methylenepropyl moieties revealed that none of the singly and doubly bridged bis-calix(n)arenes form measurable complexes with the fullerenes. A calix(5)arene singly bridged at the upper rims with a 2-butenyl spanner and carrying allyl groups at all of the other available p-positions was found to be effective.

A study was conducted to test whether the bridged carbocationic species is an intermediate or a transition state. The study also analyzed the linear/bridged ion energy gap and examine the state of helical and nonhelical precursors during the degenerate 1,2-aryl rearrangements. Experimental results indicated that the state of bridged species on the potential energy surface for the rearrangement correlated with substituents.

The claims of V. Franzen and H.-I. Joshek that thermolysis of di-1-naphthyldiazomethane in naphthalene yields dibenzofluorene and that thermal cleavage of tetra-1-naphthylehylene produces two carbenes were made in 1960. These conclusions were proven wrong and the concept of ethylenization of diarylcarbinols by treating the compound with phosphoric acid was not substantiated.

Vinylcarbenes are examined using flash vacuum pyrolysis reactions of 3,5-diphenylpyrazole and 3(5)-methyl-5(3)-phenylpyrazole. Different rearrangements in the vinylcarbene intermediate gave rise to the reaction products expected for nitrogen extrusion. Kinetic parameters for nitrogen extrusion from 3,5-diphenylpyrazole were studied to determine the influence of different substituents on the activation energy of vinylcarbene, finding out that the reaction is sensitive to substituent effect. The role of the different substituents in vinylcarbene rearrangement is also explored.

The rearrangement of substituted epoxides catalyzed by indium(III) chloride was investigated. A simple and efficient method in which aryl-substituted epoxides isomerize with complete regioselectivity to produce a single carbonyl complex via cleavage of benzylic aldehydes and ketones was proposed. Experimental results showed that indium(III) chloride exhibits a high level of efficiency in causing the rearrangement of epoxides to the corresponding carbonyl compounds in a very selective manner.

Precursors to reactive intermediates that rearrange have been applied widely in mechanistic probe studies wherein one seeks to implicate a reactive intermediate by the detection of rearranged products. The calibration of ultrafast 2-arylcyclopropylcarbinyl radical clocks has permitted quantitative applications of hydrocarbon precursors in studies of enzyme-catalyzed hydroxylation reactions. The PTOC-selenol method may be used fur indirectly determining the kinetics of the rearrangement of radicals.

A study was conducted to determine the stereochemistry of the photo-Arbuzov rearrangement of benzylic phosphites under a direct irradiation environment. 1H and 13C nuclear magnetic resonance chemical shifts were determined in parts per million against internal tetramethylsilane. Results indicated that combination was four times as fast as rotation in a first approximation. Findings also showed that product phosphonate was consistent with the production of phosphinoyl radical.

The chemistry and intramolecular reactivity of free tert-butylphenylmethylene were investigated experimentally and computationally. Free carbene tert-butylphenylmethylene was obtained via thermal rearrangement of p-tert-butylphenylmethylene and the chemistry of tert-butylphenylmethylene was modified by the introduction of a phenyl group. Results showed that the phenyl group reduces the difference in barriers between intramolecular C-H and C-C insertion from 3.6 to 2 kilocalories per molecule.

The rearrangement of a 16alpha,17alpha-epoxy-16beta-methylandrostane-17beta-carbothioic acid (2b) in solution at ambient temperature to a 17beta-mercapto-16beta-methylandrostane-17alpha,16alpha-carbolactone (6a) was described. 6a was found to have undergone almost complete decomposition after prolonged storage in the solid phase at ambient temperature in the dark. The rearrangement of 2b happens possibly through the spirocyclic alpha-thiolactone 5.

A study was conducted to determine the photochemistry of 9,9'-bifluorene-9,9'-diol and to characterize the photochemical pinacol rearrangement associated in neutral solutions. The Perkin-Elmer 1310 spectrometer was utilized to determine infrared spectra with KBr pellets. Results indicated that the photoexcitation of 9,9'-bifluorene-9,9'-diol supported a pinacol rearrangement.

A study was conducted to analyze the (2,3)-Wittig rearrangement of E and Z-allylic stannyl ethers obtained from an isopropylidene D-ribose derivative. The initial stereochemical assignment of the rearranged syn product was correlated with previous stereochemical studies. Results indicated that the (2,3)-rearrangement of Z-allylic stannyl ether proceeded with syn selectivity and very good isolated yield.

Experiments described the cyclobutene radical cation (CB)+ ring opening and its conrotatory stereochemistry in the butadiene radical cation (BD)+ product. The CB ring opening was observed in two competing pathways which resulted to cis- and trans- BD+. The 298K activation enthalpies for the two processes differed only by less than i kcal/mol. Moreover, a transition state was found to exist in the bicyclobutane radical cation conversion to CB+.

The potential energy surface for fragmentation and rearrangement of {CH3CH2OCH2}+ was characterized using high level ab initio computations implemented at the G2 level. The ion-neutral complexes are important in the lowest-energy decomposition that result in the removal of water. The values obtained from RRKM computations on the G2 surface agreed well with experimental values obtained for metastable ion elimination products as well as findings of different deuterium- and 13C-labeling studies.

Research was conducted to examine the coupling of cobalt-carbon bond homolysis and hydrogen atom abstraction in adenosylcobalamin-dependent glutamate mutase. Stopped-flow spectroscopy was used to measure the rate of substrate-induced cleavage of AdoCbl by glutamate mutase using various concentrations of glutamate and methylaspartate. Results provide insight into a mechanism in which Co-C bond homolysis is coupled to substrate hydrogen abstration.

Theoretical studies on the rearrangement of alkyl aryl sulfenates to alkyl aryl sulfoxides were conducted. Three possible mechanisms, namely, a stepwise pathway involving a radical pair intermediate and two concerted pathways involving a (1s,2s) alkyl shift and a (1a,2s) alkyl shift, were taken into account. Rigorous measurements of the parent reaction were carried out to provide a reference for the highly accurate methods.

Research was conducted to establish a acid-catalyzed rearrangement of 5-bromo-3-(1-allyl-2-(3,5-dimethoxyphenyl)-ethyl)-2-cyanopyridine formed in the electrophilic cyclization of substituted cyanopyridine. Another objective was for the identification of the intermediate products and a possible reaction mechanism for the development of the rearrangement products. Results suggest that the acid-catalyzed rearrangement of the allyl cyanopyridine proceeds with a high degree of stereoselectivity resulting in the formation of single diastereoisomers as products.

The first enantioselective synthesis of the cis-2-carboxy-5-phenylpyrrolidine is described. The synthesis showed that the (3,3) sigmatropic rearrangement of trichloroacetimidates obtained from monoprotected allylic diols provides access to 2,5-disubstitute dpyrrolidines by an approach which allows the potential to functionalize the 3,4-positions of the pyrrolidine ring.

Research was conducted to examine the influence of chelation during the diastereoselective addition of the allylindium reagent to 2- and 3-hydroxycyclohexanones in aqueous, organic, and mixed solvent systems. Results present no evident opportunity for chelation control. On the other hand, excellent stereoselectivity was observed upon axial orientation of the 3-OH group which is attributed to electronic or steric effects or the combination of both.