William G. Dauben

Bio: William G. Dauben is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Ring (chemistry) & Organic reaction. The author has an hindex of 42, co-authored 357 publications receiving 7084 citations. Previous affiliations of William G. Dauben include Hoffmann-La Roche & Lawrence Berkeley National Laboratory.

The Stereochemistry of Hydride Reductions

Abstract: I t has been shown that reductions of alkylcyclohexanones with lithium aluminum hydride, sodium borohydride and aluminum isopropoxide lead to increasing proportions of the axial (unstable) isomer. The mechanism of the reduction step is discussed with reference to the ease of formation of the initial metallo-organic complex (steric approach control) and to the relative energetics of the formation of the products once the complex is formed (product development control).

Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis

Abstract: A fundamental aim in the field of catalysis is the development of new modes of small molecule activation. One approach toward the catalytic activation of organic molecules that has received much attention recently is visible light photoredox catalysis. In a general sense, this approach relies on the ability of metal complexes and organic dyes to engage in single-electron-transfer (SET) processes with organic substrates upon photoexcitation with visible light. Many of the most commonly employed visible light photocatalysts are polypyridyl complexes of ruthenium and iridium, and are typified by the complex tris(2,2′-bipyridine) ruthenium(II), or Ru(bpy)32+ (Figure 1). These complexes absorb light in the visible region of the electromagnetic spectrum to give stable, long-lived photoexcited states.1,2 The lifetime of the excited species is sufficiently long (1100 ns for Ru(bpy)32+) that it may engage in bimolecular electron-transfer reactions in competition with deactivation pathways.3 Although these species are poor single-electron oxidants and reductants in the ground state, excitation of an electron affords excited states that are very potent single-electron-transfer reagents. Importantly, the conversion of these bench stable, benign catalysts to redox-active species upon irradiation with simple household lightbulbs represents a remarkably chemoselective trigger to induce unique and valuable catalytic processes. Open in a separate window Figure 1 Ruthenium polypyridyl complexes: versatile visible light photocatalysts.

The energy gap law for radiationless transitions in large molecules

Abstract: In this paper we present a unified treatment of non-radiative decay processes in large molecules which involve either electronic relaxation between two electronic states or unimolecular rearrangeme...

Lipids and lipid-based formulations: optimizing the oral delivery of lipophilic drugs

Abstract: Highly potent, but poorly water-soluble, drug candidates are common outcomes of contemporary drug discovery programmes and present a number of challenges to drug development - most notably, the issue of reduced systemic exposure after oral administration. However, it is increasingly apparent that formulations containing natural and/or synthetic lipids present a viable means for enhancing the oral bioavailability of some poorly water-soluble, highly lipophilic drugs. This Review details the mechanisms by which lipids and lipidic excipients affect the oral absorption of lipophilic drugs and provides a perspective on the possible future applications of lipid-based delivery systems. Particular emphasis has been placed on the capacity of lipids to enhance drug solubilization in the intestinal milieu, recruit intestinal lymphatic drug transport (and thereby reduce first-pass drug metabolism) and alter enterocyte-based drug transport and disposition.