tetrahydrobenzo[b]pyran derivatives 1 were utilized for the synthesis of several new pyrano[2,3-d]pyrimidine derivatives 2. compound 2 was obtained in the presence of ac2o/h2so4 (as a catalyst) and was confirmed by spectroscopic data such as ir, 1h nmr and 13c nmr. ab initio calculation was carried out to study geometric optimization, thermodynamic parameters, aromaticity and dynamic process of...

We explore the possibility for elemental analysis by NMR. To keep the efficiency of the signal acquisition common for all spin species, we propose to fix the frequency and vary the magnetic field to cover the isotopes involved in a sample. We introduce constant-frequency receptivity for quantitative elemental analysis in the frequency-fixed NMR experiment. Field-variable NMR experiments are dem...

background celiac disease (cd) is a disorder associated with body reaction to gluten. after the gluten intake, an immune reaction against the protein occurs and damages villi of small intestine in celiac patients gradually. objectives the osc, a filtering method for minimization of inter- and intra-spectrometer variations that influence on data acquisition, was applied to biofluid nmr data of c...

we have evaluated the nmr shielding tensors for a:t,g:c,a:u in watson-crick, and u-quartet. we have computed nmr shielding tensors at b31yp level by using 6-31g(d) basis set. we have compute anisotropy and asymmetry in a:t,g:c,a:u and u-quartet. the nmr shielding tensors were calculated using the giao method. the natural bonding orbital analysis (nbo) were performed. nbo calculation have been ...

2-amino-substituted ketones react with α-methylene ketones under solvent-free conditions at 90 °c in thepresence of a catalytic amount of zirconium dodecylphosphonate to create the corresponding quinolinesin excellent yields. this procedure recommends numerous advantages such as easy work-up, use of mild,reusable and safe catalyst, short reaction timeand high yields. the new compounds have been...

: 1h nmr spectra of a series of enaminones r-co-ch=c(nhch2ph)-r  [1, r=ch3; 2, r=c6h5; 3, r=cf3; 4, r=ch2ch2ch2; 5, r=ch2c(ch3)2ch2], were obtained in the presence of trifluoroacetic acid in cdcl3 or dmso-d6 at 28 °c. steric, solvent, electronic and hydrogen bonding effects on the rates of acid-catalyzed nh proton exchanges were investigated. rate constants were calculated by 1h nmr line shape ...