Tetramethyl-m-benziporphodimethene and isomeric alpha,beta-unsaturated gamma-lactam embedded N-confused tetramethyl-m-benziporphodimethenes.
The condensation reaction of alpha,alpha'-dihydroxy-1,3-diisopropylbenzene, pyrrole, and an aldehyde leads to the formation of tetramethyl-m-benziporphodimethene and outer alpha-pyrrolic carbon oxygenated N-confused tetramethyl-m-benziporphodimethenes containing a gamma-lactam ring in the macrocycle. Two isomers with the carbonyl group of the lactam ring either close to (O-Up) or away from (O-Down) the neighboring sp(3) meso carbon were synthesized and characterized. The single crystal X-ray diffraction analysis on the regular and gamma-lactam containing tetramethyl-m-benziporphodimethenes showed highly distorted macrocycles for all compounds. For O-Up and O-Down isomers, dimeric structures, assembling by intermolecular hydrogen-bonding interactions through lactam rings, were observed in the solid state. Fitting the concentration dependent chemical shifts of the outer NH proton using the non-linear regression method give a maximum association constant of 108.9 M(-1) for the meso 4-methylcarboxyphenyl substituted O-Down isomer. The DFT calculations concluded that the O-Up isomer is energetically more stable, and the keto form is more stable than the enol form.
Chang
Gao-Fong
GF
Institute of Chemistry, Academia Sinica, 128 Academia Road Sec. 2, Nankang, Taipei 11529, Taiwan.
Kumar
Anil
A
Ching
Wei-Min
WM
Chu
Han-Wei
HW
Hung
Chen-Hsiung
CH