13C NMR studies of some complex natural oxygen heterocyclics : Structure of millettin,a novel isoflavone isolated from Millettia Auriculata

¹³C NMR spectra for a variety of isoflavones are presented and analysed. The novel isoflavone, Millettin (Xa) is shown to be closely related to Auriculatin (II). While comparison of the ¹³C NMR spectra did not readily prove the orientation of the fused pyran ring, the use of acetylation shifts showed unambiguously that the fusion in linear, rather than angular.     

Cleavage of N?O bonds in 1,2,4-oxadiazolines

The photochemical cleavage of the N-O bond in 1,2,4-oxadiazolines I to form acetamidines II was found to occur under mild conditions (ordinary light, 3560Å, or 2537Å). The weak N-O bond in 3-mcthyl-4,5-diphenyl-1,2,4-oxadiazoline (If) was also cleaved by catalytic reduction to give a molecular compound composed of benzyl alcohol and N-phenylacetamidine, V.     

Characterization of Encapsulating Materials for Fiber Bragg Grating-Based Temperature Sensors

Abstract

An experimental study has been carried out for the characterization of encapsulating materials for fiber Bragg grating-based temperature sensors to prevent the formation of micro-cracks and devitrification on the fiber surface at elevated temperatures by making use of a rigid probe. The developed sensor probe was configured by encapsulating a type 1 fiber Bragg grating with an aluminum nitride tube and is used to measure temperatures from 20°C to 500°C. The adapted encapsulation technique validated the sensor to achieve linearity of 99.979%, sensitivity of 14.03 ± 0.02 pm/°C, and good repeatability; its practical use in harsh environments is predicted.     

A New and Facile Synthesis of Chroman-3-ols, 3,4-Dihydro-2H-[1]-Benzopyran-3-ols

o-Allyl phenols react with m-chloroperoxybenzoic acid (m-CPBA) in dry chloroform to give chroman-3-ols in a single step in good yields (93–96%).     

Search for physiologically active compounds

Proceedings - Mathematical Sciences - The synthesis of 2-[4-(1, 3-diphenyl)-pyrazolyl]-3-hydroxychromones has been carried out by AFO oxidation of 2-hydroxy-[4-(1,...     

A New and Convenient Synthesis of 3-Hydroxychromones

An improved synthesis of 3-hydroxychromones is described.