Enantiomerically Pure Cyclobutane Derivatives and Their Use in Organic Synthesis

Lee‐Ruff, Edward; Mladenova, Gabriela

doi:10.1021/cr010013a

Cited by 520 publications

(148 citation statements)

References 201 publications

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“…The structures of 6 and 7 were confirmed by 1D-NMR and 2D-NMR spectroscopic analyses, i.e. 1 H, 13 Figure 3). In the H-C HMBC spectrum (Figure 4), the correlation of H d (δ 2.98) and the cyclic carbonyl carbon (δ 219.7) was observed in the major isomer of the products, indicating that the major product was the tricyclic cyclobutane 6.…”

Section: Introductionmentioning

confidence: 74%

“…The strained cyclobutane [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and oxetane [21][22][23] structures are important in organic synthesis. After Ciamician discovered the first example of photochemical [2+2] cycloaddition reaction, 24 Paternò, following Ciamician, reported the first photochemical [2+2] oxetane formation reaction using light irradiation.…”

Section: Introductionmentioning

confidence: 99%

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Photochemical [2+2] cycloaddition reaction of enone derivatives with 2-silyloxy-1H-pyrrole derivatives

Xue¹,

Takagi²,

Abe³

2017

Arkivoc

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The regio-and stereo-selectivity of the photochemical [2+2] cycloaddition reaction of 2-(t-butyldimethylsilyloxy)-1H-pyrrole with enone derivatives are investigated. Regioselective formation of cyclobutanes was found in the intermolecular photochemical [2+2] cycloaddition reaction of the pyrrole derivative with cyclopentenone. In contrast, an oxetane rather than a cyclobutane product was selectively formed when 1,4-naphthoquinone was used as the enone. The reaction conditions were optimized to obtain the cycloadducts in high yields.

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Section: Introductionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Photochemical [2+2] cycloaddition reaction of enone derivatives with 2-silyloxy-1H-pyrrole derivatives

Xue¹,

Takagi²,

Abe³

2017

Arkivoc

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“…Of these, [2+2] photocycloadditions are especially important for the generation of highly strained cyclobutanes [5,6]. These structures are often used in the total synthesis of biologically active compounds [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Diastereoselective [2+2] Photocycloaddition of a Chiral Cyclohexenone with Ethylene in a Continuous Flow Microcapillary Reactor

et al. 2012

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The diastereoselective [2+2] photocycloaddition of ethylene to a chiral cyclohexenone was studied in a continuous flow microcapillary reactor. In all cases examined, the microcapillary reactor gave higher conversions and selectivity than the batch system, even after shorter irradiation times. These findings were explained by the superior temperature control, favorable light penetration, and generation of a gas-liquid slug flow with improved mass transfer in the microreactor.

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“…[1][2][3][4] We recently found a new synthetic utility of cyclobutanones: β′-chloro or β′,γ′-unsaturated enolates were readily prepared by titanium(IV) chloride-mediated ring cleavage of cyclobutanones. Thus, the four-membered ring of 3,3-dial kylcyclobutanone 1 was cleaved by treatment with titanium(IV) chloride to form trichlorotitanium enolate 2 having a tert-alkyl chloride group.…”

mentioning

confidence: 99%

Titanium(IV) Chloride-Mediated Ring Cleavage and Michael Addition of 3,3-Dialkylcyclobutanones and 3-[(Trimethylsilyl)methyl]-cyclobutanones

Okuno

Matsuo

Ishibashi

2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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β′-Chloro and β′,γ′-unsaturated trichlorotitanium enolates, which were formed in situ by titanium(IV) chloride-mediated ring cleavage of 3,3-dialkylcyclobutanones and 3-[(trimethylsilyl)methyl]cyclobutanones, reacted with enones to give Michael adducts with keeping a labile β′-chloro or β′,γ′-unsaturated group.Key words cyclobutanone; Michael addition; enone; ring cleavage Facile ring expansion, ring contraction and ring cleavage of cyclobutanones have been utilized in the synthesis of target molecules. [1][2][3][4] We recently found a new synthetic utility of cyclobutanones: β′-chloro or β′,γ′-unsaturated enolates were readily prepared by titanium(IV) chloride-mediated ring cleavage of cyclobutanones. Thus, the four-membered ring of 3,3-dial kylcyclobutanone 1 was cleaved by treatment with titanium(IV) chloride to form trichlorotitanium enolate 2 having a tert-alkyl chloride group. The enolate 2 reacted with aldehyde to afford the corresponding aldol product 3 5) (Eq. 1). Also, ring cleavage of 3-[(trimethylsilyl)(TMS) methyl]-cyclobutanone 4 with titanium(IV) chloride gave β′,γ′-unsaturated titanium enolate 5, which reacted with aldehyde to give a β′,γ′-unsaturated aldol product 6 6) (Eq. 2). The reactivity of an enolate bearing an easily eliminative chloride group at the β′-position (like 2) and an easily isomerizable β′,γ′-unsaturated bond 7,8) (like 5) has been unknown except for aldol reactions 5,6) because such enolates are difficult to prepare from the parent carbonyl compounds. To investigate the versatility of these functionalized titanium enolates, we studied their Michael addition 9-11) with enones, and we report here the results we obtained.First, ring cleavage of 3,3-dialkylcyclobutanones followed by Michael addition to enones was investigated (Table 1). Addition of titanium(IV) chloride to a mixture of methyl vinyl ketone (MVK) and 3,3-dimethylcyclobutanone 7 bearing a (tert-butyldimethylsilyl)(TBS) methyl group at the 2-position gave an expected Michael adduct 8a having a tert-alkyl chloride group in 69% yield (entry 1). Cyclobutanone 7 was preferentially activated with titanium(IV) chloride in the presence of MVK though it was reported that enones reacted with titanium(IV) chloride to form β-chloro enolate in the Michaelaldol and the Morita-Baylis-Hillman reaction.12,13) The use of two equivalents of MVK was required to obtain 8a efficiently because 1-tert-butyldimethylsilyl-5-chloro-5-methylhexan-3-one, which was formed by ring-cleavage of 7, was obtained along with 8a in the case of using less than two equivalents of enones. A similar reaction of 7 with pent-1-en-3-one (entry 2) and 5-phenylpent-1-en-3-one (entry 3) gave the corresponding adducts 8b and 8c in 68% and 39% yields, respectively. Though 3-methylpent-3-en-2-one also reacted with 7 to afford 8d in 53% yield (entry 4), cyclic enones such as cyclopentenone and cyclohexenone did not give Michael adduct 8. These

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Enantiomerically Pure Cyclobutane Derivatives and Their Use in Organic Synthesis

Cited by 520 publications

References 201 publications

Photochemical [2+2] cycloaddition reaction of enone derivatives with 2-silyloxy-1H-pyrrole derivatives

Photochemical [2+2] cycloaddition reaction of enone derivatives with 2-silyloxy-1H-pyrrole derivatives

Diastereoselective [2+2] Photocycloaddition of a Chiral Cyclohexenone with Ethylene in a Continuous Flow Microcapillary Reactor

Titanium(IV) Chloride-Mediated Ring Cleavage and Michael Addition of 3,3-Dialkylcyclobutanones and 3-[(Trimethylsilyl)methyl]-cyclobutanones

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