메뉴 건너뛰기




Volumn 2, Issue 12, 2000, Pages 1709-1712

α,β-epoxy vinyl triflates in Pd-catalyzed reactions

Author keywords

[No Author keywords available]

Indexed keywords

ALKANESULFONIC ACID; ANTINEOPLASTIC AGENT; LACTONE; MESYLIC ACID DERIVATIVE; PALLADIUM; PHENAZINE DERIVATIVE; SPIRO COMPOUND; STEROID;

EID: 0034658842     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol000064e     Document Type: Article
Times cited : (21)

References (42)
  • 2
    • 85037493706 scopus 로고    scopus 로고
    • Epoxide 2a was synthesized from the commercially available steroid, hecogenin in seven steps. The detailed experimental procedure is shown in the Supporting Information
    • Epoxide 2a was synthesized from the commercially available steroid, hecogenin in seven steps. The detailed experimental procedure is shown in the Supporting Information.
  • 5
    • 85037508128 scopus 로고    scopus 로고
    • 3SnH, see ref 7
    • 3SnH, see ref 7.
  • 9
    • 0000278319 scopus 로고
    • It was reported that in the case of 1-acetoxy-2-bromo-2-alkenes, the bromo substituent dramatically reduces the reactivity of the olefin in Pd-catalyzed substitutions, and that coupling between bromoalkenes and terminal alkynes proceeds without side reactions with acetoxy substituents. (a) Nwokogu, G. C. Tetrahedron Lett. 1984, 25, 31, 3263.
    • (1984) Tetrahedron Lett. , vol.25 , Issue.31 , pp. 3263
    • Nwokogu, G.C.1
  • 11
    • 0033531676 scopus 로고    scopus 로고
    • Similarly, it was recently reported that Pd-catalyzed carbonylation of 1-acetoxy-2-bromo-2-alkenes proceeds without involvement of the allylic ester. Trost, B. M.; Oslob, J. D. J. Am. Chem. Soc. 1999, 121, 3057.
    • (1999) J. Am. Chem. Soc. , vol.121 , pp. 3057
    • Trost, B.M.1    Oslob, J.D.2
  • 12
    • 85037517109 scopus 로고    scopus 로고
    • 3b gave a mixture of unidentifiable products, presumably due to acid sensitivity of vinyl epoxide
    • 3b gave a mixture of unidentifiable products, presumably due to acid sensitivity of vinyl epoxide.
  • 16
    • 85037499545 scopus 로고    scopus 로고
    • Because of the difficulty in separation from starting material, 4a was not isolated in most cases. An alternative way to make this compound is described in the Supporting Information
    • Because of the difficulty in separation from starting material, 4a was not isolated in most cases. An alternative way to make this compound is described in the Supporting Information.
  • 20
    • 85037514005 scopus 로고    scopus 로고
    • 12 although Pd-catalyzed reduction has also been described. In our case, addition of more than 1 equiv of the hydride resulted in a mixture of products resulting from over-reduction of the allyl epoxide, along with 4, 7, and 5. Addition of additional Pd catalyst had no effect on the reaction
    • 12 although Pd-catalyzed reduction has also been described. In our case, addition of more than 1 equiv of the hydride resulted in a mixture of products resulting from over-reduction of the allyl epoxide, along with 4, 7, and 5. Addition of additional Pd catalyst had no effect on the reaction.
  • 22
    • 85037519152 scopus 로고    scopus 로고
    • It is speculated that the steric repulsion between C12 TBS group of 14a suppresses its formation, resulting in the lower ratio. (matrix presented)
    • It is speculated that the steric repulsion between C12 TBS group of 14a suppresses its formation, resulting in the lower ratio. (matrix presented)
  • 23
    • 85037514628 scopus 로고    scopus 로고
    • 17(20) olefin in steroids is hydrogenated from the α-face, the C17 configuration in 17 is R, as shown (matrix prsented)
    • 17(20) olefin in steroids is hydrogenated from the α-face, the C17 configuration in 17 is R, as shown. (matrix prsented)
  • 24
    • 85037515727 scopus 로고    scopus 로고
    • The high regioselectivity in the reduction of 4a compared to 4b can be explained by the relative stability of the isomeric πallyl palladium species in each case. It is likely that 13 is more stable than 12 because of less steric repulsion between the steroidal core. However, sterics between Pd ligand and bulky TBS protecting group at C12 (see 13a) could invert the relative stability. Transmetalation and reductive elimination gives the reduced compounds, of which the ratio should reflect the energy difference between 12 and 13. (matrix presented)
    • The high regioselectivity in the reduction of 4a compared to 4b can be explained by the relative stability of the isomeric πallyl palladium species in each case. It is likely that 13 is more stable than 12 because of less steric repulsion between the steroidal core. However, sterics between Pd ligand and bulky TBS protecting group at C12 (see 13a) could invert the relative stability. Transmetalation and reductive elimination gives the reduced compounds, of which the ratio should reflect the energy difference between 12 and 13. (matrix presented)
  • 26
    • 85037498832 scopus 로고    scopus 로고
    • 4. It is assumed that the major isomer is the one with the β-configuration at C16, 7a. (matrix presented)
    • 4. It is assumed that the major isomer is the one with the β-configuration at C16, 7a. (matrix presented)
  • 27
    • 85037507264 scopus 로고    scopus 로고
    • 3-SnH gave different products depending on substrates
    • 3-SnH gave different products depending on substrates.
  • 31
    • 85037514562 scopus 로고    scopus 로고
    • 8c
    • 8c
  • 32
    • 85037503867 scopus 로고    scopus 로고
    • 8c
    • 8c
  • 33
    • 0001467798 scopus 로고    scopus 로고
    • For β-elimination of Pd-methoxide to form "Pd-H", (a) Grushin, V. V. Chem. Rev. 1996, 96, 2011.
    • (1996) Chem. Rev. , vol.96 , pp. 2011
    • Grushin, V.V.1
  • 37
    • 85037500594 scopus 로고    scopus 로고
    • 23a the corresponding reaction with aldehydes is not precedented
    • 23a the corresponding reaction with aldehydes is not precedented.
  • 38
    • 85037503612 scopus 로고    scopus 로고
    • 27 We therefore speculate that the intramolecular version of this transformation may be possible
    • 27 We therefore speculate that the intramolecular version of this transformation may be possible.
  • 42
    • 85037501642 scopus 로고    scopus 로고
    • 3SnH
    • 3SnH.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.