The use of ∝-diazo-γ-butyrolactone in the Büchner-Curtius-Schlotterbeck reaction of cyclic ketones: A facile entry into spirocyclic scaffolds

The first example of the Büchner-Curtius-Schlotterbeck reaction of cyclic ketones with a stabilized cyclic diazo compound partner is described. The approach towards spirocyclic scaffolds has been exemplified with readily available ∝-diazo-γ-butyrolactone. The reaction proved to be viable with BF₃?OEt₂ as the preferred catalyst and displayed substantial sensitivity to the size of the cyclic ketone.     

Novel access to 2-substituted quinolin-4-ones by nickel boride-mediated reductive ring transformation of 5-(2-nitrophenyl)isoxazoles

Reductive ring transformation of 3-substituted 5-(2-nitrophenyl)isoxazoles, readily accessible via 1,3-dipolar cycloaddition of 2-ethinylnitrobenzene with nitrile oxides, opens a novel access to 2-substituted quinolin-4-ones. Nickel boride, generated in situ from nickel chloride and sodium borohydride, allows, via simultaneous reduction of the nitro group and reductive cleavage of the isoxazole ring, the one-step conversion into the target quinolin-4-ones. This protocol tolerates various functional groups, except olefins, and thus is complementary to the reductive ring transformation with iron/acetic acid, which predominantly tolerates olefins.     

Ring current and anisotropy effects on OH chemical shifts in resonance-assisted intramolecular H-bonds

Ring current effects on resonance-assisted and intramolecularly bridged hydrogen bond protons for 10-hydroxybenzo[h]quinoline 1 and a number of related compounds were calculated and the through-space NMR shieldings (TSNMRS) obtained hereby visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. These calculations revealed that this through-space effect is comparably large (up to 2?ppm) dependent on the position of the intramolecularly bridged OH proton, and therefore, contribute considerably to the chemical shift of the latter making it questionable to use δ(OH)/ppm in the estimation of intramolecular hydrogen bond strength without taking this into account. Furthermore, the anisotropy effects of additional groups on the aromatic moiety (e.g. the carbonyl group in salicylaldehyde or in o-hydroxyacetophenone of ca. 0.6?ppm deshielding) should also be considered. These through-space effects need to be taken into account when using OH chemical shifts to estimate hydrogen bond strength.     

一类l-半群的l-自同构

设R有1的全序环。记Mn(R)为R上n×n矩阵乘法半群,则Mn(R)在通常格序下成为l-半群。本文对l-半群Mn(R)的∨-自同构,∧-自同构以及l-自同构给出了详细的刻画。     

A total synthesis of 11-O-methyldebenzoyltashironin

A concise total synthesis of 11-O-methyldebenzoyltashironin is reported in which oxidative dearomatization-IMDA-RCM triad constitutes the key ring forming steps, while an unorthodox DIBAL-H mediated stereo- and regioselective reductive epoxide openings and implementation of the vinyl bromide-carbonyl equivalency concept were pivotal to the success of this endeavor.     

香港大屿山残坡积土的残余强度试验研究

粘性土的残余强度是边坡稳定性评价、桩基与土的相互作用机理研究及填土边坡设计中的重要参数。本文在综述大量文献的基础上，结合香港大屿山火山岩风化残坡积土的残余强度试验研究，分析了残余强度的测试方法和影响残余强度的因素。研究结果表明，残余强度与有效法向应力间具有明显的非线性关系；与单剪测试结果相比，多级剪测试结果明显偏高。     

Synthesis of 5-trichloromethyl-Δ-1,2,4-oxadiazolines and their rearrangement into formamidine derivatives

A series of 5-trichloro-Δ⁴-1,2,4-oxadiazolines have been synthesised by 1,3-dipolar cycloaddition of nitrones to trichloroacetonitrile. These oxadiazolines rearrange into formamidine derivatives, via ring opening and a 1,2-aryl shift from carbon to the adjacent amino nitrogen. Both cycloaddition and rearrangement are facilitated when electron deficient nitriles and electron rich nitrones are used.     

Rearrangement of 3,5-dicyano-1,4-dihydropyridines to densely functionalized cyclopentadienes

3,5-Dicyano-1,4-dihydropyridines underwent ring contraction to give functionalized cyclopentadienes upon treatment with trifluoroacetic anhydride.     

Associativity of the <Emphasis Type=Italic>∇</Emphasis>-operation on bands in rings

Given a multiplicative band of idempotents S in a ring R, for all e,f∈S the ∇-product e ∇ f=e+f+fe−efe−fef is an idempotent that lies roughly above e and f in R just as ef and fe lie roughly below e and f. In this paper we study ∇-bands in rings, that is, bands in rings that are closed under ∇, giving various criteria for ∇ to be associative, thus making the band a skew lattice. We also consider when a given band S in R generates a ∇-band.     

A Simple Theoretical Model for Ring and Nanotube Radial Breathing Mode

The radial breathing modes (RBMs) of (MgO)_n and (BeO)_n rings (n=3-10) were calculated using the density functional theory at B3LYP/6-31G(d) level. It was found that for large rings, the radial breathing mode (RBM) frequency was inversely proportional to the centre diameter, but the variation of bond length may lead to deviations from a linear behavior. The deviations caused by inverse cubic term of diameter and variation of bond length, became dramatic with the decrease of ring diameter. From the point of chemical bond view, using one-dimensional harmonic oscillator and the method of cascade and parallel connection of “springs”, the linear relation and deviations were explained. The model can be applied to nanotubes.