Phosphine-Catalyzed Formation of Carbon-Sulfur Bonds: Catalytic Asymmetric Synthesis of gamma-Thioesters

Supporting Information Available: Experimental procedures and compound characterization data. This material is available free of charge via the Internet at http://pubs.acs.org.A method for catalytic asymmetric γ sulfenylation of carbonyl compounds has been developed. In the presence of an appropriate catalyst, thiols not only add to the γ position of allenoates, overcoming their propensity to add to the β position in the absence of a catalyst, but do so with very good enantioselectivity. Sulfur nucleophiles are now added to the three families of nucleophiles (carbon, nitrogen, and oxygen) that had earlier been shown to participate in catalyzed γ additions. The phosphine catalyst of choice, TangPhos, had previously only been employed as a chiral ligand for transition metals, not as an efficient enantioselective nucleophilic catalyst.National Institutes of Health (U.S.)National Institute of General Medical Sciences (U.S.) (R01-GM57034)Merck & Co.Novartis (Firm

Spin Glass and Antiferromagnetic Behaviour in a Diluted fcc Antiferromagnet

We report on a Monte Carlo study of a diluted Ising antiferromagnet on a fcc lattice. This is a typical model example of a highly frustrated antiferromagnet, and we ask, whether sufficient random dilution of spins does produce a spin glass phase. Our data strongly indicate the existence of a spin glass transition for spin--concentration $p<0.75$: We find a divergent spin glass susceptibility and a divergent spin glass correlation length, whereas the antiferromagnetic correlation length saturates in this regime. Furthermore, we find a first order phase transition to an antiferromagnet for $1\ge p>0.85$, which becomes continuous in the range $0.85>p>0.75$. Finite size scaling is employed to obtain critical exponents. We compare our results with experimental systems as diluted frustrated antiferromagnets as ${\rm Zn_{1-p}Mn_{p}Te}$.Comment: 29 pages (revtex) and 10 figures uuencoded and Z-compresse

Apšvietimas kaip architektūros modernumo simbolis

The paper is designed to reveal the aesthetics of artificial lighting and its influence on the architecture of the 20th century. The main topics discussed are electric lighting, which appeard in our history at the end of the 19th century, and the technical development of lighting till the middle of the 20th century. Connections of artificial lighting with visual arts, its influence on advertisement, building architecture and the whole city are analysed. An idea is proposed that although lighting by nature was purely functional, very soon it acquired symbolic ambitions to represent architecture. In modern times architects understood that lighting was both a technological development and a symbol of a new era, when there appeared an independent field of creation - lighting architecture. Santrauka Straipsnyje nagrinėjama dirbtinio apšvietimo estetika ir jos įtaka XX a. architektūrai. Išryškinta XIX a. pabaigoje atsiradusio elektrinio apšvietimo svarba ir atskleista apšvietimo techninė raida iki XX a. vidurio. Nagrinėjamos dirbtinio apšvietimo sąsajos su vizualiaisiais menais, apšvietimo įtaka reklamai, pastatų architektūrai bei visam miestui. Straipsnyje keliama idėja, kad nors apšvietimo prigimtis pradžioje buvo grynai funkcionali, ji greitai įgavo simbolinių ambicijų – reprezentuoti architektūrą. Architektai į apšvietimą žvelgė ne tik kaip į technologinę pažangą, tai buvo naują erą ženklinantis simbolis, erą, kurioje atsiranda didelės įtakos visoms kūrybinėms idėjoms turinti nauja savarankiška kūrybos sritis – šviesos architektūra. First Published Online: 22 May 2013 Reikšminiai žodžiai: meninis, dirbtinis, elektrinis apšvietimas, stiklo, šviesos architektūra, modernumas

Schumpeter: Theorist of the Avant-Garde

This paper argues that Schumpeter’s 1911 edition of ‘Theory of Economic Development’ can be fruitfully read as a theory of the avant-garde, in line with such theories developed by artistic avant-garde around the same time, in particular by the Italian Futurists. In particular it will show that both Schumpeter and other avant-garde theorists sought to break with past (1), identify an avant-garde who could force that break (2), find new ways to represent the dynamic world (3), embrace the new and dynamic (4) and promote a perpetual dynamic process, instead of a specific end-state or utopia (5). This new reading helps us to understand the cultural meaning of this seminal text in economics. Secondly it greatly facilitates our understanding of the differences with the later interwar German edition and English edition, which were more cautious in their embrace of the new, less focused on the individual qualities of the entrepreneur and placed more emphasis on historical continuity. Thirdly this reading suggests a different reason for the bifurcation between Schumpeter and the rest of the Austrian school of economics. Traditionally this split is explained by Schumpeter’s affinities with the Lausanne School, this paper instead suggests that the crucial break between Schumpeter on the one hand and Böhm-Bawerk, Wieser and later members of the Austrian School on the other hand is their theory of and attitude toward social change

Large transient nonproton ion movements in purple membrane suspensions are abolished by solubilization in Triton X-100.

Light-induced release/uptake of both protons and other ions cause transient changes in conductivity in suspensions of purple membrane (PM) fragments (Marinetti, Tim, and David Mauzerall, 1983, Proc. Natl. Acad. Sci. USA, 80:178-180). We find that the release/uptake of nonproton ions with quantum yield greater than 1 is observed at most pHs and ionic strengths. Only at both low pH and low ionic strength is the conductivity transient mostly due to protons. Our hypothesis is that during the photocycle, changes occur in the PM's dense surface charge distribution that result in changes in the number of counterions bound or condensed at the membrane surface. To test this, the PM structure was perturbed with the nonionic detergent Triton X-100. Immediately after addition, Triton does not abolish the nonproton ion movements; in fact at low detergent concentrations (0.02% vol/vol) the signal amplitudes increased considerably. However, when PM is completely solubilized into monomers in Triton, the conductivity transients are due to protons alone, though at lower quantum yield compared with native PM. These results suggest that changes in the surface charge distribution in native PM's photocycle could contribute to proton transfer between the aqueous phase and bR itself

Role of steric strain in the chemistry of phosphiranes

The reaction of transient [MeP-W(CO)5] with norbornene gives the two corresponding exo phosphiranes with W syn or anti to the norbornane bridge. The syn complex is selectively decomplexed by carbon monoxide at 120 °C under 50 bar. Both complexes are easily cleaved by Pd(OAc)2 at room temperature to give [MeP(OAc)2)]W(CO)5