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.

Diastereoselective Propionitrile Oxide Cycloaddition Reactions With Some γ-Substituted α-Methylene-γ-butyrolactones

1993 ◽  
Vol 46 (9) ◽  
pp. 1401 ◽  
Author(s):  
SM Pereira ◽  
GP Savage ◽  
GW Simpson ◽  
RJ Greenwood ◽  
MF Mackay
Keyword(s):  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Relative Stereochemistry

A number of γ-substituted α-methylene-γ-butyrolactone derivatives underwent 1,3-dipolar cycloaddition with propionitrile oxide to give spiro Δ2-isoxazolines. The reaction proceeded regiospecifically and with high diastereoselectivity. The products of anti addition predominated. The regiochemistry of addition and relative stereochemistry of the products were determined by a combination of n.O.e ., HETCOR and DOUBTFUL n.m.r. experiments. The assignment was confirmed in one case by X-ray crystallography.

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.

scholarly journals Exocyclic Enamines of Pyrrolo[1,2-a]quinoxalines Generated by 1,3-dipolar Cycloaddition Reactions of Benzimidazolium Ylides to Activated Alkynes

2001 ◽  
Vol 71 (3) ◽  
pp. 197-209 ◽  
Author(s):  
Alina Nicolescu ◽  
Emilian Georgescu ◽  
Florea Dumitrascu ◽  
Florentina Georgescu ◽  
Florina Teodorescu ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
X Ray ◽  
Multinuclear Nmr ◽  
X Ray Crystallography ◽  
Mild Conditions ◽  
Quinoxaline Derivatives ◽  
Multinuclear Nmr Spectroscopy ◽  
Activated Alkynes

The reactions of N-acetonylbenzimidazolium chlorides with various activated alkynes, in the presence of bases, led under mild conditions to a mixture of pyrrolo[1,2-a]benzimidazoles (3), 4-methylene-pyrrolo[1,2-a]quinoxaline derivatives (4) and pyrrolo[1,2-a]quinoxalin-4-one derivatives (5). The exocyclic enamine derivatives 4 have been fully characterized by multinuclear NMR spectroscopy and X-ray crystallography. A mechanism rationalizing the formation of the enamine derivatives is proposed.

scholarly journals Utilization of 1-phenylimidazo[1,5-a]quinoline as partner in 1,4-dipolar cycloaddition reactions

2020 ◽  
Vol 75 (3) ◽  
pp. 259-267
Author(s):  
Areej M. Jaber ◽  
Jalal A. Zahra ◽  
Mustafa M. El-Abadelah ◽  
Salim S. Sabri ◽  
Monther A. Khanfar ◽  
...  
Keyword(s):  
Single Crystal ◽  
Spectral Data ◽  
Cycloaddition Reaction ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Dimethyl Acetylenedicarboxylate ◽  
X Ray ◽  
X Ray Crystallography

AbstractA Selected set of 2-(quinolin-2-yl)-1,3-oxazepino[7,6-b]indoles 4a–d and dihydroacenaphtho[1,2-f][1,3]oxazepine 5 have been prepared via 1,4-dipolar cycloaddition reaction involving 1-phenylimidazo[1,5-a]quinoline, dimethyl acetylenedicarboxylate, and N-(substituted)isatins or acenaphthoquinone. Structures of the new heterocycles 4a–d and 5 are supported by NMR and HRMS spectral data, and confirmed by single-crystal X-ray crystallography for 4c and 5.

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