TY  - JOUR
A1  - Szatmari, Istvan
A1  - Belasri, Khadija
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
A1  - Fulop, Ferenc
T1  - Ortho-Quinone methide driven synthesis of new O,N- or N,N-Heterocycles
JF  - ChemistryOpen : including thesis treasury
N2  - To synthesize functionalized Mannich bases that can serve two different types of ortho-quinone methide (o-QM) intermediates, 2-naphthol and 6-hydroxyquinoline were reacted with salicylic aldehyde in the presence of morpholine. The Mannich bases that can form o-QM and aza-o-QM were also synthesized by mixing 2-naphthol, 2-nitrobenzaldehyde, and morpholine followed by reduction of the nitro group. The highly functionalized aminonaphthol derivatives were then tested in [4+2] cycloaddition with different cyclic imines. The reaction proved to be both regio- and diastereoselective. In all cases, only one reaction product was obtained. Detailed structural analyses of the new polyheterocycles as well as conformational studies including DFT modelling were performed. The relative stability of o-QMs/aza-o-QM were also calculated, and the regioselectivity of the reactions could be explained only when the cycloaddition started from aminodiol 4. It was summarized that starting from diaminonaphthol 25, the regioselectivity of the reaction is driven by the higher nucleophilicity of the amino group compared with the hydroxy group. 12H-benzo[a]xanthen-12-one (11), formed via o-QM formation, was isolated as a side product. The proton NMR spectrum of 11 proved to be very unique from NMR point of view. The reason for the extreme low-field position of proton H-1 could be accounted for by theoretical calculation of structure and spatial magnetic properties of the compound in combination of ring current effects of the aromatic moieties and steric compression within the heavily hindered H(1)-C(1)-C(12b)-C(12a)-C(12)=O structural fragment.
KW  - ortho-quinone methide (o-QMs)
KW  - modified Mannich reaction
KW  - cycloaddition
KW  - NMR spectroscopy
KW  - conformational analysis
KW  - DFT calculations
Y1  - 2019
U6  - https://doi.org/10.1002/open.201900150
SN  - 2191-1363
VL  - 8
IS  - 7
SP  - 961
EP  - 971
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Umbreen, Sumaira
A1  - Linker, Torsten
T1  - Simple Synthesis of Conformationally Fixed Glycosamine Analogues by Beckmann Rearrangement at the Carbohydrate Ring
JF  - Chemistry - a European journal
N2  - Conformationally fixed carbohydrate analogues are promising small-molecule inhibitors for hydrolases like O-GlcNAcase (OGA); however, their synthesis usually requires many steps. Herein we describe cycloadditions of dichloroketene to various glycals and subsequent Beckmann rearrangements, which offer an easy and stereoselective entry to glycosamine derivatives in good yields. The reactions are applicable for hexoses, pentoses, and disaccharides, and transformations to the corresponding imidates proceed smoothly. First biological tests reveal that such imidates indeed inhibit human OGA.
KW  - carbohydrates
KW  - cycloaddition
KW  - enzyme inhibitors
KW  - rearrangement
KW  - selective syntheses
Y1  - 2015
U6  - https://doi.org/10.1002/chem.201406546
SN  - 0947-6539
SN  - 1521-3765
VL  - 21
IS  - 20
SP  - 7340
EP  - 7344
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kafka, Stanislav
A1  - Hauke, Sylvia
A1  - Salcinovic, Arjana
A1  - Soidinsalo, Otto
A1  - Urankar, Damijana
A1  - Kosmrlj, Janez
T1  - Copper(I)-Catalyzed [3+2] Cycloaddition of 3-Azidoquinoline-2,4(1H,3H)-diones with terminal alkynes
JF  - Molecules
N2  - 3-Azidoquinoline-2,4(1H,3H)-diones 1, which are readily available from 4-hydroxyquinolin-2(1H)-ones 4 via 3-chloroquinoline-2,4(1H, 3H)-diones 5, afford, in copper(I)-catalyzed [3 + 2] cycloaddition reaction with terminal acetylenes, 1,4-disubstituted 1,2,3-triazoles 3 in moderate to excellent yields. The structures of compounds 3 were confirmed by (1)H and (13)C-NMR spectroscopy, combustion analyses and mass spectrometry.
KW  - cycloaddition
KW  - azides
KW  - quinoline-2,4(1H,3H)-diones
KW  - terminal alkynes
KW  - 1,2,3-triazoles
Y1  - 2011
U6  - https://doi.org/10.3390/molecules16054070
SN  - 1420-3049
VL  - 16
IS  - 5
SP  - 4070
EP  - 4081
PB  - MDPI
CY  - Basel
ER  -