title: Absolute Configuration Determination of 2,3-Dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles Using Chiroptical Methods at Different Wavelengths.
abstract: A correlation between the absolute configuration and chiroptical properties of nonracemic 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles was studied. A series of 16 novel representatives were prepared by Cu-catalyzed [3 + 2] cycloadditions of racemic (Z)-2-benzylidene-5-oxopyrazolidin-2-ium-1-ides to tert-butyl (S)-(3-oxopent-4-yn-2-yl)carbamate, and their structures were determined by NMR, VCD, ECD, and X-ray diffraction. A clear correlation between the sign of specific rotation and configuration at position C(1) allows for easy determination of the absolute configuration of 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by ECD and NMR. While VCD, requiring milligram quantities, allowed the determination of the correct relative and absolute configuration without additional information from other methods, the stereochemical analysis by ECD required knowledge of the relative configuration derived from NMR at a comparable computational level.
authors: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors: Eva
authors: E
authors: Pušavec Kirar
authors: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors: Uroš
authors: U
authors: Grošelj
authors: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors: Amalija
authors: A
authors: Golobič
authors: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors: Franc
authors: F
authors: Požgan
authors: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz , Duesbergweg 10-14, D-55128 Mainz, Germany.
authors: Stefan
authors: S
authors: Pusch
authors: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz , Duesbergweg 10-14, D-55128 Mainz, Germany.
authors: Carina
authors: C
authors: Weber
authors: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz , Duesbergweg 10-14, D-55128 Mainz, Germany.
authors: Lars
authors: L
authors: Andernach
authors: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors: Bogdan
authors: B
authors: Štefane
authors: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz , Duesbergweg 10-14, D-55128 Mainz, Germany.
authors: Till
authors: T
authors: Opatz
authors: Faculty of Chemistry and Chemical Technology, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors: Jurij
authors: J
authors: Svete