Asymmetric Catalysis with Ethylene. Synthesis of Functionalized Chiral Enolates
作者:Souvagya Biswas、Jordan P. Page、Kendra R. Dewese、T. V. RajanBabu
DOI:10.1021/jacs.5b10364
日期:2015.11.18
Trialkylsilyl enol ethers are versatile intermediates often used as enolate surrogates for the synthesis of carbonyl compounds. Yet there are no reports of broadly applicable, catalytic methods for the synthesis of chiral silyl enol ethers carrying latent functionalities useful for synthetic operations beyond the many possible reactions of the silyl enol ether moiety itself. Here we report a general
Investigation of the asymmetric ionic Diels–Alder reaction for the synthesis of cis-decalins
作者:James C. Anderson、Alexander J. Blake、Jonathan P. Graham、Claire Wilson
DOI:10.1039/b305116a
日期:——
limited subset of cis-decalin structures. Diastereoselectivities of 73% and 82% have been found for the asymmetric ionic Diels-Alder reaction between the chiral acetal derivatives of cyclohex-2-enone (6) and 2-methylcyclohex-2-enone (18) with 2,3-dimethyl-1,3-butadiene (7). Terminal substituents on the diene partner in general render the system unreactive. However a synthetically useful cis-decalin 31
[GRAPHICS]The synthesis, of lairdinol A, a component of the host-selective phytotoxin depsilairdin, was achieved in 12 steps overall yield) without the use of protecting groups starting with the Diels-Alder reaction of (R)-carvone with 3-trimethylsilyloxy-1,3-pentadiene. The key step established the trans ring fusion by preferential epoxidation of a trans-fused enone in an equilibrating mixture of the cis-fused and transfused diastereomers (i.e., equivalent to a dynamic kinetic resolution of these isomers). The synthesis confirms the absolute configurations of lairdinol A and its enantiomer, cyperusol C.
A Novel <i>Cis</i>-Selective Cyclohexanone Annulation as the Key Step of a Total Synthesis of the Sesquiterpene Isoacanthodoral
作者:Thomas Hampel、Reinhard Brückner
DOI:10.1021/ol9018979
日期:2009.11.5
Isoacanthodoral (1) is a structurally unique sesquiterpene in that it is a bicyclo[4.4.0]dec-1-ene with a cis-rather than the common trans-junction between the constituting rings. An efficient construction of this motif has been accomplished by a novel cis-selective cyclohexanone annulation, combining the lithium enolate of ester 8, the alpha,beta-unsaturated ester 6, and vinylmagnesium bromide in a single synthetic operation. For completing the total synthesis of 1, a Shapiro-olefination/hydrogenation sequence and a reductive cyanation were employed.
[4+2] Cycloadditions of Seven‐Membered‐Ring trans‐Alkenes: Decreasing Reactivity with Increasing Substitution of the Seven‐Membered Ring
作者:John Santucci、Jillian R. Sanzone、K. A. Woerpel
DOI:10.1002/ejoc.201600329
日期:2016.6
in [4+2] cycloadditions depends on the substitution pattern on the seven-membered ring. Unhindered trans-alkenes undergo [4+2] cycloadditions with 1,3-diphenylisobenzofuran faster than the most reactive trans-cyclooctene. Increasing the substitution of the seven-membered ring or increasing the electron density of the trans-alkene decreases reactivity with 1,3-dienes in concerted cycloaddition reactions