Palladium(II)-Catalyzed Cycloisomerization of Functionalized 1,5-Hexadienes
摘要:
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
摘要:
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.
A new method for the mild radical hydrosilylation of alkenes and alkynes is described. Silylated cyclohexadienes that can be readily prepared on large scale are used as radical hydrosilylating reagents. Non-activated alkenes and alkynes are hydrosilylated in high yields. The reaction can be combined with CC bond formation, as demonstrated for the preparation of silylated cycloalkanes from the corresponding
描述了烯烃和炔烃的温和自由基氢化硅烷化的新方法。可以容易地大规模制备的甲硅烷基化环己二烯被用作自由基氢化硅烷化试剂。非活化烯烃和炔烃以高产率氢化硅烷化。该反应可以与 CC 键的形成相结合,如从相应的二烯制备甲硅烷基化环烷烃所证明的那样。此外,自由基氢化硅烷化与β-断裂反应相结合用于合成烯丙基硅烷和醛和酮的氢化硅烷化提供受保护的醇可以很容易地通过该策略进行。
Stereoselective Synthesis of Tri- and Tetrasubstituted Allylsilanes via Copper-Catalyzed Decarboxylative Silylation of Vinylethylene Carbonates
作者:Wenzhu Ren、Yifei Yan、Yinhua Huang
DOI:10.1021/acs.joc.3c01297
日期:2023.12.15
Herein, a stereoselective copper-catalyzed decarboxylative silylation of readily available vinylethylene carbonates (VECs) with PhMe2Si-Bpin is reported, affording a wide range of tri- and tetrasubstituted allylsilanes in moderate to highyields with E-selectivity. This protocol was characterized by highstereoselectivity, broad substrate scope, operational simplicity, and mild reaction conditions
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.