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101.
Density functional theory calculations at the Becke3LYP level have been performed to study structural isomers of borane adducts of Cp2M(H) (M=Nb, Ta). Results of calculations show that O- and N-substituted borane adducts can have various structural isomers including boryl, hydridoborate and σ-complex structures. H-, alkyl- and Cl-substituted borane adducts are found to adopt hydridoborate structures. The structural feature is closely related to how the electron-deficient boron center is electronically saturated. 相似文献
102.
Wolfgang Reischl Elisabeth Altmann Erich Zbiral 《Monatshefte für Chemie / Chemical Monthly》1982,113(4):427-438
The possibility of regio- and stereospecific oxidation of the 7-double bond of the 4-phenyl-1,2,4-triazolin-3,5-dione adducts1 a and1 b of Vitamin D3 is reported. Oxidation of the corresponding benzoates2 a and2 b withm-Chlorperbenzoic acid yields the two oxirans3 a and3 b which in turn with NaI-CH3COOH-Zn after saponification to5 a and5 b lead to the allylic alcohols6 a and6 b. 相似文献
103.
Ottaviani P Giuliano M Velino B Caminati W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):538-543
The 1:1 molecular complex between oxetane and water has been investigated by using free-jet millimeter-wave spectroscopy. The rotational spectra of five isotopomers (with H(2)O, D(2)O, DOH, HOD and H(2) (18)O) have been assigned. Partial r(0) and r(s) structures of the complex have been derived. The water moiety lies in the plane of symmetry of oxetane, with the "free" hydrogen E with respect to the ring. The oxetane ring appears to be slightly nonplanar, with the C(beta) carbon tilted on the opposite side of the water unity. The three atoms involved in the hydrogen bond adopt a linear arrangement with an O(ring).H distance of about 1.86 A, and the angle between the COC bisector and the O(ring).H bond being congruent with 106 degrees. Additionally, quantum-chemical calculations for the complex were performed and were found to be in agreement with the experimental results. 相似文献
104.
Ka Young Lee 《Tetrahedron letters》2006,47(6):977-980
Regioselective synthesis of 1-arylnaphthalene derivatives was carried out from N-tosylaziridines, which was made from the reaction of N-tosylimines and cinnamyl bromides by using the sulfur ylide chemistry. 相似文献
105.
Seong Jin Kim 《Tetrahedron letters》2007,48(6):1069-1072
3,5,6-Trisubstituted α-pyrones were synthesized starting from the Baylis-Hillman adducts. The synthesis was carried out via the sequential introduction of ketone at the primary position of Baylis-Hillman adduct, lactonization, and the following oxidation with PCC. 相似文献
106.
Polysubstituted phenol derivatives were synthesized regioselectively starting from the Baylis-Hillman adducts via the formal [4+2] annulation protocol as the key step. 相似文献
107.
Ka Young Lee 《Tetrahedron letters》2007,48(11):2007-2011
An expeditious synthetic method of 3-arylidenelactams was developed starting from N-tosylaziridines, which were made from the reaction of N-tosylimines and cinnamyl bromides by using the sulfur ylide chemistry. The regioselective ring-opening reaction of N-tosylaziridines with anilines, as external nucleophiles, and the following lactamization afforded 3-arylidenelactams. In the absence of external nucleophiles, intramolecular lactonization occurred to afford 3-arylidenelactones. 相似文献
108.
Mochul"skaya N. N. Andreiko A. A. Kodess M. I. Vasil"eva E. B. Filyakova V. I. Gubaidullin A. T. Litvinov I. A. Sinyashin O. G. Aleksandrov G. G. Charushin V. N. 《Russian Chemical Bulletin》2004,53(6):1279-1289
The reactions of 3-aryl-1,2,4-triazines with aromatic thioamides and 4-arylthiosemicarbazides in acetic anhydride at room temperature afforded cyclic products of the tandem nucleophilic addition reactions, viz., tetrahydrothiazolo[4,5-e]-annelated 1,2,4-triazines, in good yields. The latter underwent aromatization in the presence of potassium permanganate. 相似文献
109.
Z. Hussain 《Chromatographia》2006,63(7-8):327-330
A high-performance liquid chromatography (HPLC) method for the separation of geometric and positional isomers is described.
A gas chromatography-mass spectrometry (GC-MS) method for the detection and evaluation of various isomers is described. The
developed method was able to separate the isomers in the purity range of 97.96% to 99.3% (GC analysis).
Revised: 16 November 2005 and 9 March 2006 相似文献
110.
Visible-light-induced aerobic oxidative cyanation of aza-Baylis–Hillman (aza-BH) adducts providing valuable allylic cyanides in good to excellent yields has been developed. The protocol involves in situ formation of 4π conjugated iminium ion intermediates, which undergo cyanation at the γ-position to afford Michael type adducts. This is the first example of visible-light-induced catalytic functionalization of aza-BH adducts using air (O2) as an economical and ecosustainable oxidant and TMSCN as a convenient and readily available cyanide source. 相似文献