Trimethylsilyketene dialkylacetals in organic synthesis: Reactions with alkyldiazoacetates
摘要:
The reaction of trimethylsilylketene dialkylacetals with alkyldiazoacetates in the presence of Cu(acac)(2) or Rh-2(OAc)(4) results in the formation of alkyl-2,2-dialkoxy-3-trimethylsilylcyclopropane-1-carboxylates 3-8. The cycloaddition proceeds stereoselectively, giving exclusively one of two possible diastereomers. Compounds 4 and 6 are transformed by reaction with LiAIH(4), to cyclopropylmethanols 9 and 10 in high yields. All compounds have been characterized by elemental analyses, H-1, C-13 NMR and IR spectroscopy.
2,2-Di(ethoxy)vinyllithium: A synthetic equivalent of the ethyl acetate anion
作者:Heng-xu Wei、Manfred Schlosser
DOI:10.1016/0040-4039(96)00416-9
日期:1996.4
2,2-Diethoxyvinyllithium can be readily generated from 2-bromo-1,1-diethoxyethylene by treatment with butyllithium. When dissolved in tetrahydrofuran, it can be stored at −25 °C for hours, but decomposes rapidly at 0 °C.
Systematic Repression of β-Silyl Carbocation Stabilization
作者:Xavier Creary、Elizabeth D. Kochly
DOI:10.1021/jo802722z
日期:2009.3.6
intermediate cyclopropyl cation undergoes substantial ring opening since β-silyl stabilization is not large (calculated stabilization energy of 12 kcal/mol). Solvolysis rates of 2-trimethylsilylbenzocyclobutyl derivatives are not significantly enhanced by the β-trimethylsilyl group. β-Silyl stabilization of benzocyclobutenyl carbocations generated in solution has been effectively eliminated due to antiaromatic
Zaitseva, G. S.; Livantsova, L. I.; Novikova, O. P., Journal of general chemistry of the USSR, 1991, vol. 61, # 6.2, p. 1274 - 1283
作者:Zaitseva, G. S.、Livantsova, L. I.、Novikova, O. P.、Sepulveda, M. Corredor de、Petrosyan, V. S.、Baukov, Yu. I.
DOI:——
日期:——
Livantsova, L. I.; Zaitseva, G. S.; Baukov, Yu. I., Journal of general chemistry of the USSR, 1987, vol. 57, p. 624 - 625
作者:Livantsova, L. I.、Zaitseva, G. S.、Baukov, Yu. I.
DOI:——
日期:——
2-Ethoxyvinyllithiums and diethoxyvinyllithiums : what makes them stable or fragile?
作者:Manfred Schlosser、Heng-xu Wei
DOI:10.1016/s0040-4020(96)01075-7
日期:1997.2
The elusive (E)-2-ethoxyvinyllithium can be readily generated in tetrahydrofuran at -75 degrees C from (E)-1-bromo-2-ethoxyethylene by halogen/metal exchange and subsequently trapped with electrophiles. Alkylation opens a convenient entry to (E)-configurated enethers. (E)-2-Ethoxyvinyllithium decomposes rapidly at -50 degrees C whereas its (Z)-isomer, which lacks the possibility to eliminate lithium ethoxide in a favorable anti-periplanar process, is stable under the same conditions. (E)-1,2-Diethoxyvinyllithium even sustains reflux temperatures (approximately 75 degrees C). 2,2-Diethoxyvinyllithium and (Z)-1,2-diethoxyvinyllithium can be conserved at 0 degrees C although this time loss of alcoholate can occur in the anti-mode. Obviously it matters whether the energy-rich ethoxyacetylene is formed as the elimination product or simple acetylene, as in the case of (E)-2-ethoxyvinyllithium. (C) 1997, Elsevier Science Ltd.