2‐Bromo‐2‐chloro‐3‐arylpropanenitriles can be prepared by Meerwein reaction from 2‐chloroacrylonitrile and various aryldiazonium salts under copper(II) bromide catalysis. They proved to be stable compounds which form 2‐chlorocinnnamonitriles upon treatment with bases. Reaction of the title compounds with substituted thioglycolates gave substituted 3‐aminothiophenes which have not yet been accessible by other routes. Three‐component reactions with the title compound, sodium sulfide and bromonitromethane, chloroacetonitrile, or ethyl 4‐chloroacetoacetate gave 2‐nitro‐ and 2‐cyano‐substituted 3‐aminothiophenes, and thienopyridinediones in high yields and in one single step, respectively.
1,4‐Diethynylbenzene was used as conjugated all‐carbon and rigid spacer between the 2‐, 3‐ and 4‐positions of two 1‐methylquinolinium rings. Thus, for a systematic study, a series of dicationic salts with 2,2‐, 3,3‐, 4,4‐, 3,2‐, and 3,4‐interconnections of the two positive charges was prepared, in which all even‐numbered substitution patterns are conjugated, and all odd‐numbered substitution patterns are cross‐conjugated. As a consequence, conjugated/conjugated, cross‐conjugated/cross‐conjugated, and conjugated/cross‐conjugated dications have been prepared. The different combinations result in considerably different charge distributions of the positive charges within the π‐electron systems according to the rules of resonance which translate into different DFT‐calculated frontier orbital profiles and spectroscopic properties such as 13C NMR chemical shifts, IR and Raman absorptions, and the measured as well as calculated UV/Vis spectra.
Reaction of N-alkylated imidazoles with 2-chloro-4quinazolinone gave mesomeric betaines, 2-(1-alkyl-1H-imidazolium-3-yl)quinazolin-4-olates, for which three tautomeric forms of N-heterocyclic carbenes (NHCs) can be formulated, in addition to an anionic NHC after deprotonation. The NHC tautomers were trapped with sulfur, selenium, triethylborane, and triphenylborane as thiones, selenones and borane adducts, respectively. We obtained two isomers of the cyclic borane adducts, diazaboroloquinazolinones with [1,5-a] and [5,1-b]-type fusion between the quinazolinone and the diazaborole rings.[a] Scheme 3. Synthesis of the target betaines; 15 N-labeled atoms are marked in blue. Numbering. The index "b" stands for "mesomeric betaine". Scheme 4. Betaine, NHC tautomers and anionic NHC of 13. 452 stants (J C-N3 ) and by 1D 15 N NMR spectra (see Table S1 and Fig. S2, Supporting Information). The long-range 1 H-15 N couplings (J HN ) with 15 N labeled and unlabeled nitrogen atoms (at natural 15 Eur.
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