Synthesis, structures, and conformation dynamics of pyrazolotetrathiepins and related compounds studied by x-ray crystallography, dynamic NMR, and molecular orbital calculations

1987 ◽  
Vol 52 (12) ◽  
pp. 2411-2420 ◽  
Author(s):  
B. L. Chenard ◽  
D. A. Dixon ◽  
R. L. Harlow ◽  
D. C. Roe ◽  
T. Fukunaga
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Dynamic Nmr ◽  
X Ray ◽  
X Ray Crystallography ◽  
Related Compounds

Conformational analysis of picrotoxinin by N.M.R., X-ray crystallography, and molecular orbital and classical potential-energy calculations

1983 ◽  
Vol 36 (11) ◽  
pp. 2219 ◽  
Author(s):  
PR Andrews ◽  
RTC Brownlee ◽  
MF Mackay ◽  
DB Poulton ◽  
M Sadek ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Active Form ◽  
Energy Difference ◽  
Biologically Active ◽  
Molecular Orbital Calculations ◽  
X Ray ◽  
X Ray Crystallography ◽  
Potential Energy Calculations ◽  
Classical Potential ◽  
Low Energy Conformations

The conformation of the potent convulsant drug picrotoxinin has been studied by proton n.m.r., X-ray crystallography, molecular orbital calculations and classical calculations. The calculations reveal two alternative low-energy conformations, either of which is consistent with the n.m.r. data, and one of which is also observed crystallographically. The energy difference is sufficiently small to suggest that either conformation may be the biologically active form.

Dipolar Cycloaddition Reactions of Nitrilimines

1998 ◽  
Vol 51 (6) ◽  
pp. 499 ◽  
Author(s):  
James B. F. Dunstan ◽  
Gordon M. Elsey ◽  
Richard A. Russell ◽  
G. Paul Savage ◽  
Gregory W. Simpson ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Dipolar Cycloaddition ◽  
Molecular Orbital Calculations ◽  
Cycloaddition Reactions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Complex Rearrangement ◽  
Semiempirical Molecular Orbital

A series of γ-substituted α-methylidene-γ-butyrolactone derivatives underwent regiospecific 1,3-dipolar cycloaddition with N-methyl-C-phenylnitrilimine. These reactions proceeded regiospecifically and with high diastereoselectivity, generally favouring the anti diastereomer as determined by n.m.r. spectroscopy and semiempirical molecular orbital calculations. The assignment for one product was confirmed by X-ray crystallography. N-Methyl-C-phenylnitrilimine underwent regiospecific cycloaddition with a range of C=S-containing dipolarophiles. Substituted thioureas were generally unreactive as dipolarophiles, while 5-thio-substituted 1,3,4-thiadiazole-2(3H)-thiones underwent ready reaction to produce, rather than the expected cycloadducts, complex rearrangement products. The structure of one of these unusual products has been confirmed by X-ray crystallography. A series of disubstituted nitrilimines underwent regiospecific cycloaddition with thiobenzophenone; the structures of the products were confirmed by X-ray crystallography.

The Pyrolytic Rearrangement of 1-Alkynoyl-3-methylpyrazoles: Synthesis of Pyrazolo[1,5-a]pyridin-5-ols and Related Compounds

1994 ◽  
Vol 47 (6) ◽  
pp. 991 ◽  
Author(s):  
RFC Brown ◽  
FW Eastwood ◽  
GD Fallon ◽  
SC Lee ◽  
RP Mcgeary
Keyword(s):  
Carbon Chain ◽  
Ring Structure ◽  
High Yield ◽  
Methyl Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Fused Ring ◽  
Related Compounds

Flash vacuum pyrolysis of 1-(alkyn-2′-oyl)-3-methylpyrazoles at 650°/0.03 mm forms pyrazolo[1,5-a]pyridin-5-ols, often in high yield, which may bear substituents at C2, C3 or C7. In the absence of a 3-methyl group in the precursor, N-ethynylpyrazoles are formed in low yield. The formation of both types of product is interpreted as involving 3-(N-pyrazolyl)propadienones formed by N1 → N2 migration of the N-alkynoyl group with inversion of the three-carbon chain. The fused-ring structure of 2-methylpyrazolo[1,5-a]pyridin-5-ol (25) was established by X-ray crystallography of the O-benzoyl derivative (27).

Synthesis, Optical Properties, Structures and Molecular Orbital Calculations of Subazaporphyrins, Subphthalocyanines, Subnaphthalocyanines and Related Compounds

1999 ◽  
Vol 03 (06) ◽  
pp. 453-467 ◽  
Author(s):  
NAGAO KOBAYASHI
Keyword(s):  
Molecular Orbital ◽  
Magnetic Circular Dichroism ◽  
Soret Band ◽  
Ring Expansion ◽  
Molecular Orbital Calculations ◽  
Mo Calculations ◽  
Key Points ◽  
Adsorption Data ◽  
Ring Expansion Reaction ◽  
Related Compounds

The synthesis of and spectroscopic data on subazaporphyrins, subphthalocyanines, subnaphthalocyanines and their related compounds reported to date are summarized, together with the results of molecular orbital (MO) calculations from our laboratory. Thus the problems and key points in the synthesis of these subazamacrocycles and their electronic absorption and magnetic circular dichroism (MCD) spectra are discussed, together with those of the monosubstituted-type low-symmetrical phthalocyanines obtained by their ring expansion reaction. The Q bands of these subazamacrocycles are orbitally doubly degenerate, and in the Soret band region, three transitions to the orbitally degenerate state are found. The MO calculations suggest that the HOMO levels destabilize considerably while the LUMO levels change slightly with increasing size of the π system. In addition, the electronic adsorption data are reproduced by the calculation only when the two pyrrole hydrogens in the monosubstituted-type phthalocyanines are assumed to be linked to the two pyrrole nitrogens along the short axis.

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