<b>Proton Magnetic Resonance Spectra of Cyclopropane Derivatives</b>

Graham, John D.; Rogers, Max T.

doi:10.1021/ja00870a045

Cited by 108 publications

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“…This spectrum is an example of a n AzBzX system ( 2 4 ) but it appears t o be very nearly a first-order spectrum. In view of the known values of proton coupling constants in the cyclopropane ring (5)(6)(7)(8)(9)(10) and in view of our experience with first-order AzBzX spectra (3,4), this is very curious. I t can immediately be said t h a t the coupling between the A and B protons in the CHZCHZ moiety must be not more than a cycle or two in order t o give the observed spectrum (3,4).…”

Section: Introductionmentioning

confidence: 99%

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Schaefer¹,

Hruska²,

Kotowycz³

1965

Can. J. Chem.

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The analysis of cyclopropyllithium allows estimates to be made of all proton coupling constants. The exceptionally small couplings across carbon atoms 2 and 3 are examined in the context of correlations of coupling constants with the electronegativities of substituents. I t is concluded that, although the couplings involving protons attached t o the same carbon a s the substituent decrease with increasing electronegativity of the substituent, the opposite is true for couplings involving the protons attached to carbons one bond removed from t h e substituent. Individual values are suggested for the coupling constants in cyclopropane itself and these agree with the observed 13C side bands in its proton spectrum.

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Section: Introductionmentioning

confidence: 99%

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Schaefer¹,

Hruska²,

Kotowycz³

1965

Can. J. Chem.

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“…absorption maximum at 207 nm (log E 3.3) and to the fact that the n.m.r. signals closely parallel those of cyclopropane-1,1,2-tricarboxylic acid (8): the protons of the cyclopropyl-methylene group form with the cyclopropyl proton of the forniyl-substituted carbon atom 2 an ABX system, the C,-proton being, of course, also coupled with the aldehydic proton.,…”

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confidence: 66%

“…Conversely, authentic coumalic acid was transformed according to the method of Pechmann (25) into its ethyl ester 6a which was found identical to the product arising from the pyrolysis of the cyclopropyl aldehyde 3. 8 It seems logical to assume that 3-ethoxycarbonyl-a-pyrone (7) is an intermediate in the formation of ethyl coumalate (6a) from the formyl cyclopropane dicarboxylate 3. While n o plausible mechanism for the direct formation o f the 5-substituted a-pyrone 6a can be advanced, the transformation of the cyclopropane derivative 3 to 3-ethoxycarbonyl-a-pyrone (7) can be rationalized readily (cf.…”

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confidence: 99%

α-Pyrones. II. The Synthesis of α-Pyrones From α,β-Unsaturated Aldehydes. Part II

Engel¹,

Krassny²,

Bélanger³

et al. 1973

Can. J. Chem.

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It is shown that the reaction of acrolein with bromomalonate in the presence of an alkali alkoxide, leading to a 2-formylcyclopropane-I,l-dicarboxylate, may be applied to the steroid series; thus, a 20-methylene 21-aldehyde gives in excellent yield the.corresponding cyclopropane derivative. The possibility of converting such systems to a-pyrones was investigated in the case of the acrolein adduct, diethyl 2-formylcyclopropane-1. I-dicarboxylate. While its cyclopropane ring could not be isomerized to a n olefin with aluminum chloride or by reactions catalyzed by transition metals and while photolysis led t o a dihydrofuran derivative, pyrolysis in high vacuum at 550-575" afforded directly a n a-pyrone, ethyl coumalate. Evidence is put forward for the intermediacy of 3-ethoxycarbonyl-a-pyrone in this reaction.La reaction de I'acroleine avec un bromomalonate en presence d'un alcoolate alcalin, qui conduit a un formyl-2 cyclopropanedicarboxylate-l,l, peut &tre appliqute a la serie steroi'de, un 21-aldehyde 20-mCthyl6nique donnant en excellent rendement le derive cyclopropanique correspondant. Nous avons CtudiC la possibilitk de convertir de tels systemes en a-pyrones dans le cas du formyl-2 cyclopropanedicarboxylate-l,l de ditthyle, derive de I'acrolCine. Tandis que son cycle a trois chainons ne put &tre isorntrise en olefine avec le chlorure d'aluminium ou par des reactions catalyskes par des metaux de transition et tandis que sa photolyse conduisit a un derive dihydrofurannique, sa pyrolyse, a 550-575" et sous haut vide, donna directement une a-pyrone, le c o~~m a l a t e d'ethyle. Nous suggkrons I'a-pyrone 3-tthoxycarbonylke comme intermediaire dans cette reaction.Can. J. Cheni.. 51. 3163 (19731 In 1969 our laboratory reported one of the way to bufadienolides (and generally to cifirst syntheses of bufadienolides, a class of pyrones) suffers only from the relatively low steroids comprising highly active cardiotonics, yield of the dehydrogenation step which, in our which are characterized by an a-pyrone ring experiments, did not exceed 35% of pure prodwhose position 5 is linked to the 17P-position of uct; Pettit et al. (3) report yields of 43-60% of the steroid nucleus. The salient feature of our crude product when the dehydrogenation is synthesis (I, cf. also 2) (compare Scheme 1, pathway a) consisted in a Michael addition of diethyl malonate to a 20-methylene 21-aldehyde, the hydrolysis product of the resulting adduct being subsequently subjected to enol-lactonization with concomitant decarboxylation, and the still required double bond, in conjugation with the carbonyl function of the lactone, being then introduced by a variety of methods. This pathcarried out with sulfur.The attempt to "prefigure" the desired double bond in the form of a suitable substituent of the malonate employed (cf. Scheme 1, pathway b) is obviously problematic. The olefin-forming elimination from the addition product, involving a leaving group (X in adduct iii of Scheme I) which is ci and not P to the ester groups, could hardly be ex~ec...

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“…Under these condi tions, the former compound is not produced ( 1 H NMR spectroscopic data; for the spectrum of 1,1 dichloro 2 methoxycyclopropane, see Ref. 16), and the latter com pound is apparently unstable and is hydrolyzed with traces of water to form acrylate 11. The 1 H NMR spectra of acrylate 11 and 1,1 dichloro 2 deuterio 3 (trideuterio methoxy)prop 1 ene (12) Interestingly, the degree of deuteration at position 2 of unsaturated compounds 11 and 12 is ∼100%, although pH of the solution decreases with time (due to elimination of DCl upon the formation of acrylate 11) and reaches 2 by the end of the reaction.…”

Section: Methodsmentioning

confidence: 99%

Pathways of decomposition of N-cyclopropyl N nitrosoureas in methanol

Клименко

Tomilov

2005

Russ Chem Bull

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Decomposition of a series of N cyclopropyl N nitrosoureas (CNU) in CD 3 OD was stud ied. These decompose much more rapidly than N methyl N nitrosourea, one of the decompo sition pathways being denitrosation, which is atypical of alkylnitrosoureas under the reaction conditions used. The nature of substituents in the cyclopropane ring has a great effect on the stability of CNU and the product ratio. In the presence of H 2 SO 4 , decomposition occurs much more rapidly. Possible pathways of the formation of the major decomposition products of CNU are proposed based on the experimental data.In our recent studies 1 aimed at investigating the reac tivities of diazocyclopropanes and cyclopropanediazonium ions containing various substituents in the cyclopropane ring, we faced the problem of synthesizing N cyclopropyl N nitrosoureas (CNU) as the sources for the generation of these species. It appeared that some of these nitroso compounds decompose during storage in protic solvents. One of decomposition pathways involves denitrosation giving rise to the corresponding N cyclopropylurea. In vestigations into decomposition pathways of nitrosoureas are topical, because this class of compounds can serve as both NO donors with a broad spectrum of biological ac tivities 2 and alkylating agents (sources of diazonium ions), which either induce or, to the contrary, inhibit cancer cell growth. 3 It is important to know possible mechanisms of decomposition of nitrosoureas and reveal the factors fa vorable for a particular reaction pathway in order to eluci date their role in vivo. It should be noted that denitrosation of N alkyl N nitrosoureas containing one alkyl substitu ent at the N atom, unlike that of di and trialkyl substi tuted N nitrosoureas, is poorly studied so far. There are, actually, only two publications dealing with this reaction. N Methyl N nitrosourea (MNU) was demonstrated 4 to undergo denitrosation in aqueous solutions at pH < 1. Denitrosation of N ethyl and N methyl N nitrosoureas in the presence of piperidine or morpholine 5 was accom panied by the formation of N nitrosoamines.The available fragmentary data on decomposition of CNU in protic solvents stimulated us to perform system atic investigations of these processes. In the present study, we performed solvolysis of six N cyclopropyl N nitroso ureas in methanol and examined the influence of the substituents in the cyclopropane ring on the rate of de composition of these compounds and the product ratio. It should be noted that a thorough kinetic investigation was beyond the scope of the present study, because our cur rent aim was to compare the stabilities of various nitroso ureas and investigate their decomposition pathways. Results and DiscussionWe studied N cyclopropyl N nitrosourea (1), gem di substituted CNU containing substituents of various na ture, viz., N (2,2 dichlorocyclopropyl) (2), N (2,2 di methylcyclopropyl) (3), N (spiropentyl) (4), and

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Proton Magnetic Resonance Spectra of Cyclopropane Derivatives

Cited by 108 publications

References 0 publications

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

α-Pyrones. II. The Synthesis of α-Pyrones From α,β-Unsaturated Aldehydes. Part II

Pathways of decomposition of N-cyclopropyl N nitrosoureas in methanol

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