Microwave-assisted solvent-free intramolecular 1,3-dipolar cycloaddition reactions leading to hexahydrochromeno[4,3-b]pyrroles: scope and limitations
摘要:
We report the microwave-assisted solvent-free synthesis of hexahydrochromeno[4,3-b]pyrroles. Intramolecular 1,3-dipolar cycloadditions proceed under these conditions within 15-40 min in 16-84% yields. An influence of the microwave irradiation upon various [3+2] cycloaddition reaction intermediates was studied. Additionally, a scope and limitations of these reactions including an influence of the dipolarophile geometry upon the cycloaddition selectivity and steric demands of the dipole upon its reactivity were also disclosed. These observations led us to postulate a preferable transition state of the reaction. Finally, an influence of the microwave irradiation to the isomerization of activated olefins was also described. (c) 2006 Elsevier Ltd. All rights reserved.
Tandem Claisen Rearrangement/6-<i>endo</i>Cyclization Approach to Allylated and Prenylated Chromones
作者:Bernd Schmidt、Martin Riemer、Uwe Schilde
DOI:10.1002/ejoc.201501151
日期:2015.12
o-acylphenols reacted upon microwave irradiation to form C-allylated or -prenylated chromone derivatives, depending on the substitution pattern of the arene and the allyl substituent. The reaction proceeds through a tandemClaisen rearrangement and 6-endo-trig or 6-endo-dig cyclization sequence. For prenyl ethers, the tandem sequence can be extended by a Cope rearrangement to furnish 6-prenylchromones.
Intramolecular reactivity of functionalized arylcarbenes: 2-allyloxyphenylcarbenes
作者:Frank Gotzhein、Wolfgang Kirmse
DOI:10.1016/s0040-4039(97)00090-7
日期:1997.2
2-Allyloxyphenylcarbenes (8) undergo intramolecular addition (→ 9) and (formal) CH insertion (→ 11) competitively. Stereochemical labels indicate that 11 and major amounts of 9 arise from triplet 8. The intermolecular OH insertion of singlet 8 with methanol (neat) is ca. 50 times faster than intramolecular addition. Under these conditions, intramolecular reactions and intersystem crossing of triplet
Microwave-assisted solvent-free intramolecular 1,3-dipolar cycloaddition reactions leading to hexahydrochromeno[4,3-b]pyrroles: scope and limitations
作者:Jiří Pospíšil、Milan Potáček
DOI:10.1016/j.tet.2006.10.074
日期:2007.1
We report the microwave-assisted solvent-free synthesis of hexahydrochromeno[4,3-b]pyrroles. Intramolecular 1,3-dipolar cycloadditions proceed under these conditions within 15-40 min in 16-84% yields. An influence of the microwave irradiation upon various [3+2] cycloaddition reaction intermediates was studied. Additionally, a scope and limitations of these reactions including an influence of the dipolarophile geometry upon the cycloaddition selectivity and steric demands of the dipole upon its reactivity were also disclosed. These observations led us to postulate a preferable transition state of the reaction. Finally, an influence of the microwave irradiation to the isomerization of activated olefins was also described. (c) 2006 Elsevier Ltd. All rights reserved.
Ueber die stereochemie intramolekularer nitron-olefin-additionen