Validation of Diethoxyphosphonate as an Effective Agent for Charge Transfer in Anion Relay Chemistry (ARC)

The diethoxyphosphonate group comprises an effective agent to achieve negative charge migration in Type II Anion Relay Chemistry (ARC). The process involves a [1,4]-phosphorus-Brook rearrangement that proceeds via a phosphacyclic intermediate leading to an anion that can be captured by reactive electrophiles. In the absence of an exogenous electrophile, the anion derived via phosphorus migration undergoes internal displacement of the phosphonate group to produce a diastereomeric mixture of cyclopropanes.     

The [1,5]-Brook rearrangement: an initial application in anion relay chemistry

The [1,5]-Brook rearrangement proceeds efficiently in a series of hydroxyl dithiane substrates with sodium and potassium bases; less effective are lithium bases. That the mode of silyl migration is intramolecular was demonstrated by a crossover experiment. Finally, the tricomponent anion relay chemistry (ARC) coupling tactic was demonstrated employing the [1,5]-Brook rearrangement.     

Affine systems inL 2 (ℝ d ) II: Dual systems

The fiberization of affine systems via dual Gramian techniques, which was developed in previous papers of the authors, is applied here for the study of affine frames that have an affine dual system. Gramian techniques are also used to verify whether a dual pair of affine frames is also a pair of bi-orthogonal Riesz bases. A general method for a painless derivation of a dual pair of affine frames from an arbitrary MRA is obtained via the mixed extension principle. This work was partially sponsored by the National Science Foundation under Grants DMS-9102857, DMS-9224748, and DMS-9626319, by the United States Army Research Office under Contracts DAAL03-G-90-0090, DAAH04-95-1-0089, and by the Strategic Wavelet Program Grant from the National University of Singapore.     

Through‐Bond/Through‐Space Anion Relay Chemistry Exploiting Vinylepoxides as Bifunctional Linchpins

The development of new bifunctional linchpins that permit the union of diverse building blocks is essential for the synthetic utility of anion relay chemistry (ARC). The design, synthesis, and validation of three vinylepoxide linchpins for through‐bond/through‐space ARC are now reported. For negative charge migration, this class of bifunctional linchpins employs initial through‐bond ARC by an S_N2′ reaction, followed by through‐space ARC exploiting a 1,4‐Brook rearrangement. The trans‐disubstituted vinylepoxide linchpin yields a mixture of E/Z isomers, whereas the cis‐disubstituted and the trans‐trisubstituted vinylepoxide linchpins proceed to deliver three‐component adducts with excellent E selectivity.     

On necessary conditions for infinite-dimensional extremum problems

In this paper, we carry on the analysis (introduced in [4] and developed in [2,7]) of optimality conditions for extremum problems having infinite-dimensional image, in the case of unilateral constraints. This is done by associating to the feasible set a special multifunction. It turns out that the classic Lagrangian multiplier functions can be factorized into a constant term and a variable one; the former is the gradient of a separating hyperplane as introduced in [4,5]; the latter plays the role of selector of the above multifunction. Finally, the need of enlarging the class of Lagrangian multiplier functions is discussed.     

Diversity-oriented synthesis of 2,4,6-trisubstituted piperidines via type II anion relay chemistry

An effective, general protocol for the Diversity-Oriented Synthesis (DOS) of 2,4,6-trisubstituted piperidine congeners has been designed and validated. The successful strategy entails a modular approach to all possible stereoisomers of the selected piperidine scaffold, exploiting Type II Anion Relay Chemistry (ARC), followed in turn by intramolecular S(N)2 cyclization, chemoselective removal of the dithiane moieties and carbonyl reductions.     

Sporolide B: Synthetic Studies

Studies directed toward the synthesis of the architecturally complex marine natural product sporolide B are described. Synthetic analysis suggested advanced hydroquinone and benzodiquinane fragments, which upon elaboration were successfully united via an ester linkage. Macrocyclization studies were then carried out, and although a novel macrocyclization product was obtained, subsequent studies revealed that the tertiary hydroxyls at C(6) and C(10) were too sterically encumbered to participate in a successful macrocyclization to furnish sporolide B.     

Reverse micellar based synthesis of ultrafine MgO nanoparticles (8-10 nm): characterization and catalytic properties

Anisotropic nanostructures of magnesium oxalate dihydrate were synthesized using cationic surfactant based microemulsion method. The cationic surfactant plays an important role in forming the anisotropic structures. The oxalate nanostructures acts as an excellent precursor for the synthesis of fine magnesium oxide nanoparticles (~10 nm). Both the precursor and the oxide were characterized by using PXRD, IR, surface area and HRTEM. The surface area of these surfactant free oxide nanoparticles was found to be 108 m(2)/g. The catalytic activity of this basic oxide was examined for the Claisen-Schmidt condensation reaction and was found to be comparable to the best reported for the conventionally prepared MgO. Chalcone formation was found to increase with time as observed using gas chromatography-mass spectrometry (GC-MS). The reusability of the catalyst was checked by using the same catalyst twice which showed a reduced percentage (50% compared to first cycle) conversion.