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Acetal

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Yasuyuki Kita – One of the best experts on this subject based on the ideXlab platform.

  • reaction of Acetals with various carbon nucleophiles under non acidic conditions cc bond formation via a pyridinium type salt
    Chemistry-an Asian Journal, 2012
    Co-Authors: Hiromichi Fujioka, Tomohiro Maegawa, Takashi Okitsu, Yoshinari Sawama, Kenzo Yahata, Tomohito Hamada, Ozora Kubo, Takuya Ohnaka, Yasuyuki Kita

    Abstract:

    Mild substitution reactions of Acetals with carbon nucleophiles via the pyridinium-type salts generated by the treatment of Acetals with TESOTf-2,4,6-collidine or 2,2′-bipyridyl have been developed. Various carbon nucleophiles, such as organocuprates, silyl enol ethers, enamines, etc., reacted with the pyridinium-type salts to give the corresponding substituted products in good yields. The reactions proceeded under very mild conditions (non-acidic conditions) and thus acid-sensitive functional groups can be tolerated during the reaction. In addition, only an Acetal can form the pyridinium-type salt and react with nucleophiles in the presence of a ketal. This unusual selectivity is in contrast to general methods conducted under acidic conditions.

  • Reaction of the Acetals with TESOTf-base combination; speculation of the intermediates and efficient mixed Acetal formation.
    Journal of the American Chemical Society, 2006
    Co-Authors: Hiromichi Fujioka, Takashi Okitsu, Yoshinari Sawama, Nobutaka Murata, Yasuyuki Kita

    Abstract:

    We report here unexpected highly chemoselective deprotection of the Acetals from aldehydes. Treatment of Acetal compounds from aldehydes with TESOTf-2,6-lutidine or TESOTf-2,4,6-collidine in CH2Cl2 at 0 °C followed by H2O workup at the same temperature caused the conversion of the Acetal functions to aldehyde functions. The reaction had generality and was applied to many Acetal compounds. Study using various bases revealed the reaction and reached the best combination of TESOTf−base. It was very mild and highly chemoselective and proceeded under weakly basic conditions. Then, many functional groups such as allyl alcohol, silyl ether, acetate, methyl ether, triphenylmethyl (Tr) ether, 1,3-dithiolane, methyl ester, and tert-butyl ester could survive under these conditions. Furthermore, this methodology could selectively deprotect the Acetals in the presence of ketals as the most characteristic feature, although this chemoselectivity is difficult to achieve by other previously reported methods. A detailed st…

Hiromichi Fujioka – One of the best experts on this subject based on the ideXlab platform.

  • reaction of Acetals with various carbon nucleophiles under non acidic conditions cc bond formation via a pyridinium type salt
    Chemistry-an Asian Journal, 2012
    Co-Authors: Hiromichi Fujioka, Tomohiro Maegawa, Takashi Okitsu, Yoshinari Sawama, Kenzo Yahata, Tomohito Hamada, Ozora Kubo, Takuya Ohnaka, Yasuyuki Kita

    Abstract:

    Mild substitution reactions of Acetals with carbon nucleophiles via the pyridinium-type salts generated by the treatment of Acetals with TESOTf-2,4,6-collidine or 2,2′-bipyridyl have been developed. Various carbon nucleophiles, such as organocuprates, silyl enol ethers, enamines, etc., reacted with the pyridinium-type salts to give the corresponding substituted products in good yields. The reactions proceeded under very mild conditions (non-acidic conditions) and thus acid-sensitive functional groups can be tolerated during the reaction. In addition, only an Acetal can form the pyridinium-type salt and react with nucleophiles in the presence of a ketal. This unusual selectivity is in contrast to general methods conducted under acidic conditions.

  • Direct conversion of Acetals to esters with high regioselectivity via O,P-Acetals
    Organic and Biomolecular Chemistry, 2011
    Co-Authors: Tomohiro Maegawa, Kazuki Otake, Akihiro Goto, Hiromichi Fujioka

    Abstract:

    A new direct conversion of O,O-Acetals to esters via O,P-Acetal intermediates was developed. The regioselective cleavage of unsymmetrical cyclic Acetals occurred to give the more crowded esters as single isomers.

  • Reaction of the Acetals with TESOTf-base combination; speculation of the intermediates and efficient mixed Acetal formation.
    Journal of the American Chemical Society, 2006
    Co-Authors: Hiromichi Fujioka, Takashi Okitsu, Yoshinari Sawama, Nobutaka Murata, Yasuyuki Kita

    Abstract:

    We report here unexpected highly chemoselective deprotection of the Acetals from aldehydes. Treatment of Acetal compounds from aldehydes with TESOTf-2,6-lutidine or TESOTf-2,4,6-collidine in CH2Cl2 at 0 °C followed by H2O workup at the same temperature caused the conversion of the Acetal functions to aldehyde functions. The reaction had generality and was applied to many Acetal compounds. Study using various bases revealed the reaction and reached the best combination of TESOTf−base. It was very mild and highly chemoselective and proceeded under weakly basic conditions. Then, many functional groups such as allyl alcohol, silyl ether, acetate, methyl ether, triphenylmethyl (Tr) ether, 1,3-dithiolane, methyl ester, and tert-butyl ester could survive under these conditions. Furthermore, this methodology could selectively deprotect the Acetals in the presence of ketals as the most characteristic feature, although this chemoselectivity is difficult to achieve by other previously reported methods. A detailed st…

Julio D Martin – One of the best experts on this subject based on the ideXlab platform.

  • synthetic studies towards ciguatoxin via Acetal γ oxovinyl stannane condensation a convergent approach
    Tetrahedron Letters, 1996
    Co-Authors: Joseluis Ravelo, Alicia Regueiro, Elsa Rodriguez, Jose De Vera, Julio D Martin

    Abstract:

    Abstract A two-directional approach converting Acetals to O-linked oxacycles, by way of intramolecular allyl tin-Acetal condensation, is described.