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Methods were developed to convert dipentaerythritol efficiently into di-[OMICRON]-benzylidene, di-[OMICRON]-cyclohexylidene, di-[OMICRON]-l-ethylpropylidene, and di-[OMICRON]-methylene diacetals. The known di-[OMICRON]-benzylidene acetal, considered to be a single isomer, was shown to be close to a statistical mixture of the cis, cis-,cis,trans-, and trans,trans-isomers. Structures were established by a combination of NMR spectroscopy and X-ray crystallography. Reaction of the di-[OMICRON]-benzylidene acetals with benzyl chloride and potassium hydroxide surprisingly gave good to excellent yields of the monobenzyl ethers. An explanation for this observation was advanced. The dibenzyl derivatives of the di-[OMICRON]-benzylidene acetals were formed by reaction of their dianions with benzyl bromide in DMF. Selective reduction of the di-[OMICRON]-benzylidene acetals with triethylsilane and boron trifluoride etherate gave 2',6'-di-[OMICRON]-benzyldipentaerythritol. A crown ether was formed in modest yield (12%) by reaction of the dianion of the di-[OMICRON]-methylene acetal with [alpha],[alpha]'-dibromo-m-xylene in DMF. Key words: dipentaerythritol, pentaerythritol, acetals, dendrimer, selective benzylation, crown ether.

Research has been conducted on the nucleophilic carbene. The reactions of this compound with diazofluorene, diphenyldiazomethane and azidotrimethylsilane have been investigated via single-crystal X-ray crystallography and the results are discussed.

Nitrate, acetate, chloride and bromide salts of the bicyclic cation [Bi(SCH2CHOH)2]+ reveal a substantial thermodynamic preference for the thiolate-alcohol chelate in a 2:1 stoichiometry. The conformational features of the cation were drammatically different in each of the the resulting molecular structures. The changes in the molecular structure of the bicyclic bis(2-hydroxyethanediol)bismuth(III) complexes were also dependent on the relative donor capabilities of the anion.

The phosphadiazonium cation (Mes*NP)+ undergoes nucleophilic additions with fluorenylidine anion Mes*NH2 and Mes*OH, where Mes* = 2,4,6-tri-tert-butylphenyl, to yield phosphaalkenes and phosphenium cations which show the insertion of the N-P moiety into the H-Y, where Y = C, N, O bonds. A general reaction mechanism is experimentally supported by the separation and characterization of a sigma-complex model of the trapped intermediate, (Mes*NP-PPh3)(SO3CF3), for the insertion mechanism.

Sterically burdened Sb N(H)(C6H2Bu3)3 and Bi N(H)(C6H2Bu3)3 are isolated and studied for their spectroscopic and structural properties. Nuclear magnetic resonance spectroscopy and x-ray crystallography are used in the experiments. Results indicate that substantial steric crowding occurs in the complexes due to the C6H2Bu3 substituents. This phenomenon causes a severe distortion from a pyramidal geometry at the pnictogen center.

Vibrational spectroscopic and x-ray crystallographic observations of two classes dithiabismuth heterocycles synthesized via quantitative metathesis were carried out. The heterocycles were chloro-substituted monocycles and tethered bicyclic derivatives. The observations revealed the occurence of monocyclic bismuthenium cations as the dominant dissociation product in their synthesis.

The effectiveness of simple sulfinyl and sulfonyl groups as electron-withdrawing protecting groups for pyrroles is analyzed using (super 13)C NMR spectroscopy and confirmed by consideration of X-ray crystal structures. The 2,4-dinitrobenzenesulfinyl and sulfonyl groups are shown to be effective electron-withdrawing protecting groups for pyrroles.

Research has been conducted on chalcogeno-urea complexes of iminophosphines. The authors describe the isolation and characterization of these complexes.

The development of green, selective, and efficient catalysts, which can aerobically oxidize a variety of alcohols to their corresponding aldehydes and ketones, is of both economic and environmental significance. Nanometer-sized hydrous RuO(sub 2) was successful incorporated into supercages of faujasite zeolite using a one-step hydrothermal synthesis.

Lawesson's reagent (LR) has been shown to react with the N-heterocyclic carbenes [1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr)] to give adducts of the general form NHC·P(S)2-C6H4OCH3. Full characterizations, including X-ray crystal structures, are provided. The reaction of Woollins' reagent (WR) with IMes gave the known selanone, (IMes)Se. [ABSTRACT FROM AUTHOR]

Lawesson's reagent (LR) has been shown to react with the N-heterocyclic carbenes [1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr)] to give adducts of the general form NHC·P(S)2-C6H4OCH3. Full characterizations, including X-ray crystal structures, are provided. The reaction of Woollins' reagent (WR) with IMes gave the known selanone, (IMes)Se. [ABSTRACT FROM AUTHOR]

Abstract: An extended π‐system containing two [3]cumulene fragments separated by a p‐carboquinoid and stabilized by two capping N‐heterocyclic carbenes (NHCs) has been prepared. Mono‐ and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4‐bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis‐1,4‐([3]cumulene)‐p‐carboquinoid as a result of the π‐accepting properties of the capping NHCs. [ABSTRACT FROM AUTHOR]