The NMR spectra of four-membered carbocyclic ring systems

Fleming, Ian; Williams, Dudley H.

doi:10.1016/0040-4020(67)85140-8

Cited by 109 publications

(35 citation statements)

References 59 publications

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“…In the case of B, the head-to-head structure 9 can be chosen immediately since the coupling constant, J = 6 Hz, of its cyclob~ityl protons shows that these must be adjacent (13). In the case of A and C, because of the chemical equivalence of the cyclobutyl protons, a direct choice between 9 and 10 cannot be made.…”

Section: Introductionmentioning

confidence: 99%

“…The possibility that one or both of thc ring fusions is trans, and that conversion to the cis fusion does not occur because of failure of the adjacent carbonyl group(s) to enolize, Can Distinction between the anti structure 13 and the syn structure 14 cannot be made directly on the basis of p.m.r. spectroscopy because of the similarity of the coupling constants between cis and trans vicinal cyclobutyl protons (13). The choice was made on the following basis.…”

Section: Introductionmentioning

confidence: 99%

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Regiospecificity and Stereoselectivity in the Photodimerization of 2,3-Dihydro-2,6-dimethyl-4-pyrone

Yates¹,

MacGregor²

1973

Can. J. Chem.

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Ultraviolet irradiation of 2,3-dihydro-2,6-dimethyl-4-pyrone in aqueous solution leads to the regiospecific and stereoselective formation of three cis-anti-cis photodimers of the cyclobutane type, i.e., octahydro-2,7-8a,8b-tetramethylcyclobuta[l,2-b:4,3-b']dipyran-4,5-diones, whose structures have been established by chemical and spectroscopic methods, including studies of nuclear Overhauser effects in the proton magnetic spectrum of one of them. The dimers undergo photointerconversion, and it is proposed that this process involves photoreversion to monomer and that the reversibility of the dimerization reaction may be a factor in determining the regiochemistry and stereochemistry of the photodimers. A bisdehydro product prepared from the dimers of the dihydropyrone has been shown to undergo photocleavage to 2,6-dimethyl-4-pyrone, and it is proposed that reversibility may also be a factor affecting the course of the photodimerization of this pyrone.Si l'on irradie la dihydro-2,3 dimethyl-2,6 pyrone-4 avec de l'ultraviolet en phase aqueuse, on observe la formation regiosptcifique et sttreoselective de trois photodimeres cis-anti-cis du type cyclobutane i.e octahydro tetramethyl-2,7,8a, 8b cyclobutadipyranne-[1,2-b:4,3-b'] diones-4,5. Ces structures ont ett elucidtes a I'aide de methodes chimiques et spectroscopiques qui incluent des etudes de I'effet Overhauser nuclkaire dans le spectre de resonance magnttique nucleaire du proton pour I'une de ces structures. Les dimtres subissent une photointerconversion dont le processus semble impliquer une photoreversion au monomere et que la reversibilite de la dimerisation peut Stre un facteur determinant dans la regiochimie et dans la stereochimie des photodimtres. Un produit bisdehydro prepare a partir de dimeres de la dihydropyrone semble subir u'n photoclivage pour donner la dimethyl-2,6 pyrone-4; il est propose que la reversibilite peut aussi Etre un facteur influencant le processus de photodimerisation de cette pyrone.[Traduit par le journal]Can.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Regiospecificity and Stereoselectivity in the Photodimerization of 2,3-Dihydro-2,6-dimethyl-4-pyrone

Yates¹,

MacGregor²

1973

Can. J. Chem.

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“…Furthermore, they vary over a sufficient range, so that some overlap between the values occurs. Due to the presence of phenyl ring appear shifted the resonance signals of cis-vicinal protons to higher field than those of trans-vicinal (Fleming & Williams, 1967;Chi et al, 1997). This is the first report to isolate such dimer from natural sources and we have given the name -diplicatin B (2) (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

“…Stereochemical information on organic compounds is usually derived from vicinal H, H coupling constants. The values of cyclobutane system vary widely with overlapping ranges from cis to trans couplings (Fleming & Williams, 1967). Psoralea plicata Del.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Density Functional Theory Study of a New Dimer with Tetrasubstituted Cyclobutane Ring System Isolated from Psoralea plicata Seeds

Arfaoui¹,

Al‐Ayed²,

Said³

et al. 2013

IJC

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A new cyclobutane ring system related to plicatin B has been isolated from the methanol soluble fraction of Psoralea plicata seeds and named as -diplicatin B. In addition, the anti-repellent (-)-loliolide and phloretic acid ethyl ester [3-(4-hydroxyphenyl) propanoic acid ethyl ester) have been isolated from the same extract, their structures being determined on the basis of 1D ( 1 HNMR and 13 CNMR) and 2D (DQF-COSY, HMQC and HMBC) NMR and mass spectra. Stereoisomers of -diplactin B have been optimized by means of density functional theory using the hybrid functional B3LYP.

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“…The ir spectrum of 28 shows carbonyl stretching absorptions at 1760 and 1720 cm-', while the 'H nmr spectrum exhibits a three-proton singlet (6 3.70, C02Me) and a four-proton ABMN system in the regions 6 2.57-2.78 and 6 2.91-3.08 (CH2COCH2). It is known (29) that protons on a cyclobutanone ring such as that present in 28 exhibit, in addition to the expected geminal couplings, long range couplings (both cis and trans) across the four-membered ring. While complete analysis of the coupling constants and chemical s h i f t of these four protons in 28 was not carried out, it was observed that irradiation of the higher field (6 2.57-2.78) two-proton multiplet essentially removed the large (J = 18 Hz) geminal couplings from the 6 2.91-3.08 multiplet.…”

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confidence: 99%

Total synthesis of the stemodane-type diterpenoids (±)-stemodin and (±)-maritimol. Formal total synthesis of (±)-stemodinone and (±)-2-desoxystemodinone

Piers¹,

Abeysekera²,

Herbert³

et al. 1985

Can. J. Chem.

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SUCKLING. Can. J. Chem. 63, 3418 (1985). Total syntheses of the stemodane-type diterpenoids (+-)-stemodin (2) and (2)-maritimol(4), as well as formal total syntheses of (*)-stemodinone (3) and (?)-2-desoxystemodinone (5). are described. The known ketol 12 was converted into the tricyclic enone 7. Photoaddition of allene to 7 gave (96%) a mixture of the photoadducts 20-23 (40: 51 :6: 3, respectively). Ozonolysis of 20, followed by treatment of the resultant d~one 24 with MeONa-MeOH (room temperature, 2.5 h), provided the keto ester 26 (94%). Subjection of 21 to an identical sequence of reactions gave (86%) the same product 26. On the other hand, when the dione 25 was treated with MeONa-MeOH under much milder conditions (PC, 5 min), the Isomeric keto esters 27 (39%) and 28 (33%) were produced. Both 27 and 28, upon reaction with MeONa-MeOH at room temperature, were converted efficiently into 26. Reduction (NaBH, or Lisec-BulBH) of 26 provided separable mixtures of the ester alcohol 32 and the lactone 33, which could be transformed readily into the dimesylates 35 and 39, respectively. Reaction of 35 and 39 with NaCN in warm hexamethylphosphoramide afforded the dinitriles 37 and 40, both of which, upon treatment with t-BuOK in refluxing t-BuOH, produced the same enaminonitrile 41. Acid hydrolys~s of 41 provided the dione 42. Preparatively, compound 26 could be transformed conveniently into the dione 42 (52% overall yield) without separation of mixtures of isomeric synthetic intermediates. Treatment (CH2CI2, -95°C) of 42 with MelSil-EtlN, followed by oxidation of the resultant products 46 and 47 with Pd(OAc)> in acetonitrile, gave the bis enones 48 (67%) and 49 (19%). Compound 48 was converted into the dione 52 which, upon reaction with (i-PrO)lTiMe in ether, provided an 86: 14 mixture of the keto alcohols 53 and 54 (63% from 48). Reduction (NaBH4) of 53 afforded (*)-maritimol (4). On the other hand, conversion of the 86: 14 mixture of 53 and 54 into the p-toluenesulfonylhydrazones 55 and subsequent reaction of 55 with NaH in refluxing toluene gave the alkene alcohols 56 (58%) and 57 (12%). Hydroboration-oxidation (9-BBN, refluxing tetrahydrofuran; NaOH, Hz02) of 56 afforded (88%) (*)-stemodin (2).EDWARD PIERS, BRIAN F. ABEYSEKERA, DAVID J . HERBERT et IAN D. SUCKLING. Can. J. Chem. 63, 3418 (1985). On dCcrit des synthkses totales des diterpenoi'des, du type stCmodane, (2)-stCmodine (2) et (t)-maritimol (4) ainsi que des synthkses totales formelles de la (*)-stemodinone (3) et de la (*)-dCoxy-2 stCmodinone (5). On a transform6 le cCtol connu 12 en Cnone trieyclique 7. La photoaddition de I'allkne sur 7 conduit a un mClange (96% de rendement) des photoadduits 20-23 (prCsents respectivement dans les rapports 40:51:6:3). L'ozonolyse du composC 20, suivie par un traitement de la dione 24 qui en rCsulte par du MeONa-MeOH (tempirature ambiante, 2.5 h), conduit au cCto-ester 26 (94%). Lorsqu'on soumet le composC 21 a une sCrie identique de rkactions, il y a formation du m@me composC 26 (86%). Par ailleurs, si I'on traite la...

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The NMR spectra of four-membered carbocyclic ring systems

Cited by 109 publications

References 59 publications

Regiospecificity and Stereoselectivity in the Photodimerization of 2,3-Dihydro-2,6-dimethyl-4-pyrone

Regiospecificity and Stereoselectivity in the Photodimerization of 2,3-Dihydro-2,6-dimethyl-4-pyrone

Experimental and Density Functional Theory Study of a New Dimer with Tetrasubstituted Cyclobutane Ring System Isolated from Psoralea plicata Seeds

Total synthesis of the stemodane-type diterpenoids (±)-stemodin and (±)-maritimol. Formal total synthesis of (±)-stemodinone and (±)-2-desoxystemodinone

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