Scope and limitations of the Pd(II)-catalyzed cycloisomerization of functionalized 1,5-hexadienes have been studied. In situ NMR experiments indicate a challenging competition between various reaction pathways. A careful balance between substrate structure, nature of the precatalyst, and reaction conditions was required to gain access to a useful building block for sesquiterpene total synthesis.
Sequential Homoaldolization. Cuprate Rearrangement in a Stereoselective Synthesis of Stannyl Dienes: Application to the Synthesis of the Western C10-C15 Subunit of (.+-.)-Tylosin Aglycon
作者:Patrick Le Menez、Valerie Fargeas、Isabelle Berque、Jacques Poisson、Janick Ardisson、Jean-Yves Lallemand、Ange Pancrazi
DOI:10.1021/jo00117a007
日期:1995.6
A stereospecific synthesis of stannyl diene 5, corresponding to the C10-C15 fragment of(+/-)-tylosin aglycon 2, was reported. Silyl carbamate 16, submitted to the Hoppe homoaldolization conditions with propanal, gave the anti aldol product 17 in 89% yield. Further treatment including oxidation of the silyl group led to lactone 21. The corresponding dihydrofuran 23 was then transformed into vinylstannane 25, via an efficient Kocienski rearrangement. An iodine exchange was performed on 25 and followed by a Stille coupling reaction with tributylstannyl acetylide. Stannyl cupration of the resulting silylated enyne 27 led in 44% yield to a 1:1 mixture of the desired (E,E)-stannyl diene 5b and the unexpected (E,Z) isomer 29. The same reaction performed on desilylated enyne 28 delivered in 85% yield the pure (E,E)-stannyl diene 5.
MAJETICH, GEORGE;HULL, KENNETH;CASARES, ADA M.;KHETANI, VIKRAM, J. ORG. CHEM., 56,(1991) N2, C. 3958-3973
作者:MAJETICH, GEORGE、HULL, KENNETH、CASARES, ADA M.、KHETANI, VIKRAM
DOI:——
日期:——
Cyclooctane or cyclohexane annulations based on intramolecular additions of allylsilanes to conjugated dienones
作者:George Majetich、Kenneth Hull、Ada M. Casares、Vikram Khetani
DOI:10.1021/jo00012a034
日期:1991.6
The scope and limitations of alkenyl dienone cyclizations for the formation of fused cyclooctane or cyclohexane systems are described.