Mechanism and stereochemistry of oxetane reactions. I. Stereospecific synthesis of the diastereoisomeric 2-phenyl-3-methyloxetanes and study of their configuration and conformation by nuclear magnetic resonance spectroscopy

Balsamo, Aldo; Ceccarelli, G.; Crotti, Paolo; Macchia, Franco

doi:10.1021/jo00892a021

Cited by 25 publications

(13 citation statements)

References 3 publications

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“…The H,H coupling constants between the 3‐ and 4‐methine protons were 7.1 Hz for δ = 4.95 and 5.46 ppm and 6.9 Hz and 7.0 Hz (averaged value is 7.0 Hz) for δ = 4.45 and 5.11 ppm. This confirmed that the former corresponded to the cis form and the latter to the trans form, because in 3‐methyl‐2‐phenyloxetanes the cis form has a larger coupling constant ( 3 J H,H = 8.1 Hz) than that ( 3 J H,H = 6.7 Hz) of the trans form, and the reported 1,2‐oxaphosphethanes have similar tendencies: that is, 3 J H,H = 7.5 Hz for the cis form and 3 J H,H = 5.9 Hz for the trans form . From these results, the two signals observed at δ = –57.3 and –55.2 ppm in the 31 P{ 1 H} NMR spectra were assigned to cis ‐ and trans ‐1,2‐oxaphosphetanes 5a and 5b , respectively.…”

Section: Resultssupporting

confidence: 59%

(E)‐Selective Wittig Reactions between a Nonstabilized Phosphonium Ylide Bearing a Phosphastibatriptycene Skeleton and Benzaldehydes

et al. 2016

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Wittig reactions between benzaldehyde derivatives and a nonstabilized phosphonium ylide bearing a phosphastibatriptycene skeleton, regarded as a tridentate aryl ligand, gave (E)‐alkenes with high selectivity in the presence of both lithium and sodium salts. As previously reported, reactions between a triphenylphosphonium ylide and benzaldehyde derivatives under the same conditions afforded mainly (Z)‐alkenes. Variable‐temperature (VT) 31P{1H} NMR spectra showed two signals, assigned to cis‐ and trans‐1,2‐oxaphosphetanes, which were observed at different temperatures (–80 °C and –40 °C, respectively) in the Wittig reaction between benzaldehyde and the nonstabilized phosphonium ylide bearing the phosphastibatriptycene skeleton, in the presence of both lithium and sodium salts, and showed the existence of equilibrium between these products at –40 °C. On the other hand, this equilibrium was not clearly observed in the reaction between the triphenylphosphonium ylide and benzaldehyde, for which only one signal was detected. The observed intermediates were confirmed to be 1,2‐oxaphosphetanes by deprotonation of the isolated β‐hydroxyalkylphosphonium salts bearing a phosphastibatriptycene skeleton and a triphenylphosphine moiety, respectively. Crossover reactions were conducted in the deprotonations of β‐hydroxyalkylphosphonium salts with TMS2NNa in the presence of p‐chlorobenzaldehyde, resulting in the observation of signals corresponding to 1,2‐oxaphosphetanes containing phenyl and p‐chlorophenyl groups at the 4‐positions, indicating the exchange process between benzaldehyde and p‐chlorobenzaldehyde at –40 °C for the phosphastibatriptycene system and at 0 °C for triphenyl derivatives. These results clearly indicated that stereochemical drift occurred at those temperatures, even in reactions using nonstabilized phosphonium ylides. The stereochemical drift in the phosphastibatriptycene system occurred at a lower temperature than in the case of the triphenyl derivative, thus explaining the (E)‐selective Wittig reactions between the benzaldehyde derivatives and the nonstabilized phosphastibatriptycene‐based phosphonium ylide in the presence of lithium and sodium salts.

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Section: Resultssupporting

confidence: 59%

(E)‐Selective Wittig Reactions between a Nonstabilized Phosphonium Ylide Bearing a Phosphastibatriptycene Skeleton and Benzaldehydes

et al. 2016

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“…Compound 4 was readily decomposed under the vpc conditions, but its purification was accomplished successfully by medium-pressure liquid chromatography followed by repeated vacuum distillations. The stereochemical assignment of l c , It, and 3c based on the 'H nmr data was in accordance with that deduced from the consequence of the ring closure process (5). The configurations of 2c, 2t, and 3t were assigned from the characteristics observed in the 'H nmr spectra: J2,,(cis) > J2 ,,(trans), tic2-,(cis) > tic2-,(trans), and tic3-,(cis) > tic3-,(trans).…”

Section: Introductionsupporting

confidence: 83%

“…1981 reaction (6). Since the separation and purification of l c and It obtained in the photoreaction were troublesome, they were synthesized from erythro-and threo-2-methyl-1-phenyl-3-@-toluenesulfonyloxy)-1-propanols by following the reported procedures (5). The photoreaction of benzaldehyde with 3,3-dimethyl-1-butene gave a mixture rich in 3r.…”

Section: Oxetanesmentioning

confidence: 99%

Thermal fragmentation of 3-alkyl-2-phenyloxetanes, 3,3-dimethyl-2-aryloxetanes, and related compounds. A case study of 2-aryl-substituted oxetanes

Imai¹,

Nishida²

1981

Can. J. Chem.

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TOSHIRO IMAI and SHINYA NISHIDA. Can. J. Chem. 59,2503Chem. 59, (1981. Thermolyses of epimeric 3-alkyl-2-phenyloxetanes ( l c , It, 2c, 2t, 3c, and 3t), 3,3-dimethyl-2-aryloxetanes (4, 5, 6, 7, and 8), 3,3,4,4-tetramethyl-2,2-diphenyloxetane (9), and 3,3-dimethyl-2,2-diphenyloxetane (10) were studied in degassed N , N , N ' , N 1 -tetramethylethylenediamine at 270-350°C. Although the fragmentation of 9 and 10 can be understandable on the basis of a diradical mechanism, there were several observations, in the reaction of certain other oxetanes, which could hardly be explained simply in terms of such a mechanism. Namely, ( 1 ) less strained I t reacted faster than more strained l c ; (2) a major mode of the fragmentation for l c , k , and 3c was "B" (forming an alkene and benzaldehyde), whereas that for lr, 21, and 3t was "A" (forming an alkenylbenzene and formaldehyde); (3) the apparent energy of activation for the "B" process seemed to be larger than that for the "A"; (4) a dramatic change of the major fragmentation mode from "B" to "A" was brought about by a substituent on the phenyl group, as was observed in 4-8. These results may be explained reasonably by assuming that the fragmentation proceeds, at least, in dual reaction courses. In competition with an anticipated diradical pathway, there will be another process, which is energetically little more favorable than the diradical fragmentation, rather specific to the "A" mode of fragmentation, and important particularly in the reaction of the trans isomers. Probable candidates for the second process are discussed.TOSHIRO IMAI et SHINYA NISHIDA. Can. J. Chem. 59, 2503Chem. 59, (1981.Dans la N,N,N1,N'-tetramCthylCthylknediamine dkgazke a 270-350°C on a Ctudie la thermolyse des alkyl-3 phinyl-2 oxetannes (lc, It, 2c, 2r, 3c et 3t), des dimethyl-3,3 aryl-2 oxetannes (4, 5, 6, 7 et 8) epimkres, du tetramethyl-3,3,4,4 diphenyl-2,2 oxetanne (9) et de la dimethyl-3,3 diphenyl-2,2 oxetanne (10). On peut comprendre la fragmentation des composes 9 et 10 en fonction d'un mkcanisme biradicalaire, mais certains faits observes dans la rkaction de certains autres oxktannes, ne peuvent &tre interprktks selon ce mecanisme. En particulier (I) le composk le moins encombrk It reagit plus rapidement que le composk l c plus encombre; (2) la voie principale de fragmentation de lc, 2c et 3c est la voie "B" (conduisant a un alcene et 5. la benzaldehyde) tandis que les composks It, 2t et 3t se fragmentent suivant la voie "A" (conduisant a un alcenylbenzkne et a la formaldehyde); (3) I'knergie apparente d'activation de la voie "B" semble Stre plus elevee que celle de la voie "A"; (4) dans le cas des composes 4-8 la presence d'un substituant sur le groupe phenyle provoque un changement radical dans la fragmentation qui passe de la voie "B" a la voie "A". On peut raisonablement expliquer ces resultats en admettant que la fragmentation s e fait au moins des deux f a~o n s au cours de la reaction. I1 existe un autre processus knergiquement plus favorise qui entre en competition avec la fr...

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“…Optically active 3,3-dimethyl-2-phenyl-oxetane (S)-( + )-3a has been synthesized previously by means of enantioselective reduction of 3-chloro-2,2-dimethyl-1-phenyl-1-propanone followed by ring closure. 33 In this work as well as that of Balsamo et al 15 it has been shown that the chiral center of starting substances (1,2-disubstituted 1,3-diols or 1,2-disubstituted 3-chloropropanols) is not involved in the ring closure and keeps its original configuration. The diols 1a, 1c and 1g in optically pure R and S forms were readily converted into the optically pure oxetanes (Figure 3) by the PTC procedure described above.…”

Section: Figuresupporting

confidence: 63%

“…Application of PTC methods (quaternary ammonium salt, NaOH as base, CH 2 Cl 2 as solvent) led to the formation of 3a-i (Scheme 4) in the overall yields indicated in parentheses. Compound 3a has been reported in the literature 15 and was prepared in 82 % yield from the mesylate of 1a by treatment with KOBu-t in tert-butyl alcohol following the literature method. Attempts by us (entries 2 and 3 in Table 1) to use cheaper KOH in MeOH led to significantly poorer yields.…”

Section: Scheme 2 Schemementioning

confidence: 99%

Phase-Transfer Synthesis of Optically Pure Oxetanes Obtained from 1,2,2-Trisubstituted 1,3-Propanediols

Hu¹,

Kellogg²

1995

Synthesis

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Mechanism and stereochemistry of oxetane reactions. I. Stereospecific synthesis of the diastereoisomeric 2-phenyl-3-methyloxetanes and study of their configuration and conformation by nuclear magnetic resonance spectroscopy

Cited by 25 publications

References 3 publications

(E)‐Selective Wittig Reactions between a Nonstabilized Phosphonium Ylide Bearing a Phosphastibatriptycene Skeleton and Benzaldehydes

(E)‐Selective Wittig Reactions between a Nonstabilized Phosphonium Ylide Bearing a Phosphastibatriptycene Skeleton and Benzaldehydes

Thermal fragmentation of 3-alkyl-2-phenyloxetanes, 3,3-dimethyl-2-aryloxetanes, and related compounds. A case study of 2-aryl-substituted oxetanes

Phase-Transfer Synthesis of Optically Pure Oxetanes Obtained from 1,2,2-Trisubstituted 1,3-Propanediols

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