Silenes in organic synthesis: a concise synthesis of (+/-) -epi-picropodophyllin

A concise, seven step synthesis of the aryl tetralin lignan lactone epi-picropodophyllin from piperonal is described. The key steps are a silene diene Diels-Alder reaction and the Hosomi-Sakurai reaction of the resultant silacyclohexene.     

Fast initialization of the spin state of an electron in a quantum dot in the Voigt configuration

We consider the initialization of the spin state of a single electron trapped in a self-assembled quantum dot via optical pumping of a trion level. We show that with a magnetic field applied perpendicular to the growth direction of the dot, a near-unity fidelity can be obtained in a time equal to a few times the inverse of the spin-conserving trion relaxation rate. This method is several orders of magnitude faster than with the field aligned parallel, since this configuration must rely on a slow hole spin-flip mechanism. This increase in speed does result in a limit on the maximum obtainable fidelity, but we show that for InAs dots, the error is very small.     

Square principles in ℙ<Subscript>max</Subscript> extensions

By forcing with P_max over strong models of determinacy, we obtain models where different square principles at ω ₂ and ω ₃ fail. In particular, we obtain a model of \({2^{{\aleph _0}}} = {2^{{\aleph _1}}} = {\aleph _2} + {\neg }\square \left( {{\omega _2}} \right) + {\neg }\square \left( {{\omega _3}} \right)\).     

Zinc‐Catalyzed Dual C–X and C–H Borylation of Aryl Halides

A zinc‐catalyzed combined C? X and C? H borylation of aryl halides using B₂pin₂ (pin=OCMe₂CMe₂O) to produce the corresponding 1,2‐diborylarenes under mild conditions was developed. Catalytic C? H bond activation occurs ortho to the halide groups if such a site is available or meta to the halide if the ortho position is already substituted. This method thus represents a novel use of a group XII catalyst for C? H borylation. This transformation does not proceed via a free aryne intermediate, but a radical process seems to be involved.     

Silver perchlorate induced rearrangement of a tetraarylethene involving an apparent oxygen migration

An H-shaped tetraarylethene ligand was prepared and shown to react with silver perchlorate to produce a crystalline silver complex of a rearranged ligand. X-ray crystallography revealed that this involved the formation of a phenanthrene ring system with the apparent migration of an oxygen atom. We believe that this rearrangement proceeds via the intermediacy of a spirodienone.     

One‐Pot Decarboxylative Acylation of N‐, O‐, S‐Nucleophiles and Peptides with 2,2‐Disubstituted Malonic Acids

Monocarbonyl activation of 2,2‐disubstituted malonic acids with benzotriazole leads to decarboxylation of one of the carboxy groups and formation of a C?H bond. Intermediate carbonyl benzotriazoles then readily acylate nucleophilic reagents and peptides resulting in libraries of conjugates and peptidomimetics.     

New benzotriazole-based reagents for the phosphonylation of various N-, O-, and S-nucleophiles

Benzotriazole surrogates showing higher stabilities than the corresponding chlorophosphates, allow phosphonylation of a variety of N-, O-, and S-nucleophiles in good yields.     

4,4′-Bis(2-pyridyl)-3,3′-bi-1,2,5-thia­diazo­le

The title compound, C₁₄H₈N₆S₂, crystallizes with the planes of the two central 1,2,5-thia­diazo­le rings orthogonal and with the pyridine rings approximately coplanar with their attached 1,2,5-thia­diazo­le rings.     

峰值积分法的研究与应用

本文对峰值积分法（ＰＩＭＳ）的机理作了探讨，叙述了ＰＩＭＳ法应用于中低合金钢中不同状态铝：总铝（Ａｌｒ）、酸溶铝（Ａｌｓｏｌ）和酸不溶铝（Ａｌｉｎｓ）的成份测定，方法的精密度和准确度能满足分析的要求。