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Abstract: Five cyclopentanones were prepared for the purpose of examining the effects of stereogenic centers on the course of the intramolecular [4 + 3] cycloaddition reactions of cyclopentenyl cations. One [...]

A synthesis of (S,S)-isodityrosine, a naturally occurring key structural subunit of numerous biologically active macromolecules is described. The synthesis features a novel benzannulation strategy to construct the C-O ether linkage.

A summary on the synthesis and chemistry of chiral molecular tweezers and certain related species is presented. An analysis of chiral recognition is performed using variable temperature chiral high-performance liquid chromatography.

Experimental studies of the mechanism and scope of the retro-nazarov reaction is described. This methodology developed was used for the synthesis of the natural product turmerone.

Research has been conducted on the 4+3 cycloadditions of a cyclopetenyl cation to a diene. The endo/exo selectivity in this type of cycloadditions has been examined via the theoretical experiments and the results are reported.

Research has been conducted on the cyclopentadienones. The formation of cyclopentadienone dimer and its decarbonylation are discussed.

The need to produce an analogue of Kagan's ether for the preparation of a number of ligands resulted in the synthesis of dihydroxy-5,6,11,12-tetrahydro-5,11-epoxydibenzo[a,e]cycloctene. The synthesis was accomplished in its racemic and enantiomer forms. The application of the synthetic molecules in the further synthesis of a chiral molecular square has been successfully accomplished and other possible applications are already being conducted.

Nuclear magnetic resonance (NMR)‐based screening of materials is a powerful tool for quality control, authenticity testing, and purity testing of compounds. However, reliance on 3‐(trimethylsilyl)‐propane‐1‐sulfonate (DSS) and 3‐(trimethylsilyl)propanoic acid (TMSP) for referencing the spectra of aqueous samples is not without hazard, particularly with automated analyses. The assumption that these reference signals always represent 0 ppm is ubiquitous in NMR spectroscopy and is routinely used for spectral alignment. However, it has been found that cyclodextrins readily generate inclusion complexes with DSS and TMSP with the effect of rendering this assumption incorrect. These inclusion complexes alter the electronic shielding of the trimethylsilane functional groups on DSS and TMSP yielding a small, but significant, shift to a higher frequency in the signal relied upon for spectral referencing. As a result, samples containing traces of these compounds may be incorrectly declared fraudulent, inconsistent with standards, or adulterated. In order to maintain the viability of this screening method, vigilance and/or improved referencing of spectra is needed. [ABSTRACT FROM AUTHOR]

The scope of application of allylic sulfones in the 4 + 3 cycloaddition reaction was explored through analyzing the principles involved in the synthesis of (trimethylsilyl)methyl allylic sulfones. Treatment of a trimethylsulfone with trimethylaluminum indicated that simple butadienes did not trap the intermediate cation very efficiently. This was secondary to the inherently lower nucleophilicity of the butadiene in relation to the furan. It was also indicated that the minor product in an intramolecular 4 + 3 cycloaddition yielded a product containing a cis ring fusion.

The intramolecular 4 +3 cycloaddition of oxyallylic and alkoxyallylic cations is investigated. The process is used to prepare cyclooctanoids and ingenanes. Results indicate that the cycloaddition of cyclic cations gives rise to cycloadducts stereoselectively and in fair to good yields. Moreover, a stepwise reaction involving cationic intermediates may be involved in the formation of certain cycloadducts.

The Intramolecular cycloaddition reaction between the E and Z isomers of alkoxyallylic sulfones with TiCl4 results in the formation of 4 + 3 cycloadducts indicating that cycloaddition is the fastest process of intermediate allylic cations. It is necessary to control the conformation about the bonds attaching the allylic cation and dienes to the tether for obtaining a high level of diastereoselectivity. The E isomer produces (3 + 2) cycloadduct, enol ether and (4 + 3) cycloadducts, whereas the Z isomer exclusively produces (4 + 3) isomers.

Products obtained from the intramolecular 4 + 3 cycloaddition of associated allylic cations result from the treatment of (trimethylsilyl)methyl allylic sulfones attached to a furan with trimethylaluminum. 2, 5-disubstitution on the furan prevents the development of cycloadducts, and leads to two distinct types of products which ostensibly form from ipso or ortho attack of the allylic cation on the furan ring and are succeeded by the trapping of subsequently obtained oxonium ions by trimethylaluminum.