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
T2  - 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
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/48916
SN  - 2191-1363
VL  - 8
IS  - 7
SP  - 961
EP  - 971
PB  - Wiley-VCH
CY  - Weinheim
ER  -