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Chemistry - An Asian Journal
Volumn 4, Issue 11, 2009, Pages
Dichotomous control of E/Z-geometry in intramolecular cyclization of o-alkynylbenzamide derivatives catalyzed by organic superbase P4-tBu in the presence/absence of water
Author keywords

Intramolecular cyclization; Organocatalysis; Phosphazenes; Superbase
Indexed keywords

BIOLOGICALLY ACTIVE MOLECULES; DOUBLE BONDS; INTRAMOLECULAR CYCLIZATIONS; ISOINDOLINONE; ORGANOCATALYSIS; PHOSPHAZENES; PRESENCE/ABSENCE;
EID: 73649097948     PISSN: 18614728     EISSN: 1861471X     Source Type: Journal    
DOI: 10.1002/asia.200900342     Document Type: Article
Times cited : (61)
References (47)
  • 17
    • 33750444272 scopus 로고    scopus 로고
    • For other examples
    • For other examples; a) W. Tang, Y.-X. Ding, J. Org. Chem. 2006, 71, 8489-8492;
    • (2006) J. Org. Chem. , vol.71 , pp. 8489-8492
    • Tang, W.1    Ding, Y.-X.2
  • 30
    • 5144232802 scopus 로고    scopus 로고
    • For recent examples of catalytic reactions, see
    • For recent examples of catalytic reactions, see: a) T. Imahori, C. Hori, Y. Kondo, Adv. Synth. Catal. 2004, 346, 1090-1092;
    • (2004) Adv. Synth. Catal. , vol.346 , pp. 1090-1092
    • Imahori, T.1    Hori, C.2    Kondo, Y.3
  • 38
    • 73649126327 scopus 로고    scopus 로고
    • Acetonitrile and DMSO were dried over 3 Å molecular sieves
    • Acetonitrile and DMSO were dried over 3 Å molecular sieves.
  • 39
    • 73649107722 scopus 로고    scopus 로고
    • Other solvents, such as DMF, toluene, 1,4-dioxane were investigated using 10 mol% of DBU as the catalyst, however these solvents were less effective in terms of either E/Z-selectivities or chemical yields; DMF: 96% yield, 47% Z; toluene: 19% yield, >98% Z; 1,4-dioxane: 16% yield, >98% Z
    • Other solvents, such as DMF, toluene, 1,4-dioxane were investigated using 10 mol% of DBU as the catalyst, however these solvents were less effective in terms of either E/Z-selectivities or chemical yields; DMF: 96% yield, 47% Z; toluene: 19% yield, >98% Z; 1,4-dioxane: 16% yield, >98% Z.
  • 40
    • 73649145624 scopus 로고    scopus 로고
    • The structure of the major isomer of 2a was determined to be Z by X-ray crystallographic analysis. See the Supporting Information for details
    • The structure of the major isomer of 2a was determined to be Z by X-ray crystallographic analysis. See the Supporting Information for details.
  • 42
    • 73649102201 scopus 로고    scopus 로고
    • Theoretical studies on the carboxylic acid system revealed that the participation of the carboxylic acid fragment reduced the activation energy of the transition states significantly and led to the exclusive formation of the Z-isomer. See, Ref. [10]
    • Theoretical studies on the carboxylic acid system revealed that the participation of the carboxylic acid fragment reduced the activation energy of the transition states significantly and led to the exclusive formation of the Z-isomer. See, Ref. [10].
  • 43
    • 73649097702 scopus 로고    scopus 로고
    • When DBU is employed as the catalyst, it is considered that the conjugate acid, [DBU·H]+, would serve as the proton source, thus providing (Z)-2a predominantly (Table 1, entries 1-3). To prove our hypothesis, we performed the reaction using P4-tBu (3), because this stronger base generates a much less acidic conjugate acid, [P4- tBu·H]+
    • When DBU is employed as the catalyst, it is considered that the conjugate acid, [DBU·H]+, would serve as the proton source, thus providing (Z)-2a predominantly (Table 1, entries 1-3). To prove our hypothesis, we performed the reaction using P4-tBu (3), because this stronger base generates a much less acidic conjugate acid, [P4- tBu·H]+.
  • 44
    • 73649106327 scopus 로고    scopus 로고
    • 2O co-solvent system provided a trace amount of 2a at 608C for 3 h when DBU was employed as the catalyst. An elevated temperature and prolonged reaction time were required to obtain the desired product in good yield (at 808C for 1 h: 89% yield, >98% Z)
    • 2O co-solvent system provided a trace amount of 2a at 608C for 3 h when DBU was employed as the catalyst. An elevated temperature and prolonged reaction time were required to obtain the desired product in good yield (at 808C for 1 h: 89% yield, >98% Z).
  • 45
    • 73649136610 scopus 로고    scopus 로고
    • The structure of the major isomer of 2d was determined to be E by X-ray crystallographic analysis. See the Supporting Information for details
    • The structure of the major isomer of 2d was determined to be E by X-ray crystallographic analysis. See the Supporting Information for details.
  • 46
    • 73649135517 scopus 로고    scopus 로고
    • Neither (Z)-2d nor (E)-2d isomerized to opposite geometrical stereoisomer in the presence of 10 mol% P4-tBu in dried DMSO (0.125m) at 408C for 2 h
    • Neither (Z)-2d nor (E)-2d isomerized to opposite geometrical stereoisomer in the presence of 10 mol% P4-tBu in dried DMSO (0.125m) at 408C for 2 h.
  • 47
    • 73649144647 scopus 로고    scopus 로고
    • 2O cosolvent system gave a 1:1 mixture of E/Z-isomers in 95% yield. This result strongly suggests that the tBu substituent effectively accelerates the isomerization of (Z)-2' into (E)-2' (see Table 2, entries 1-4)
    • 2O cosolvent system gave a 1:1 mixture of E/Z-isomers in 95% yield. This result strongly suggests that the tBu substituent effectively accelerates the isomerization of (Z)-2' into (E)-2' (see Table 2, entries 1-4).

* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.