When heated in refluxing benzene or toluene, α-diazo β-ketophosphonates 2, prepared in three steps from aldehydes or ketones, gave rise to functionalized cyclobutenones 4 or phenolic compounds 5. These products are formed by electrocyclisation respectively of a vinyl or dienylketene, resulting from a Wolff rearrangement.
The Synthesis of a Degradation Product of Phomazarin: A Regiospecific Elaboration of the B and C Rings of the Pigment
作者:Vincent Guay、Paul Brassard
DOI:10.1055/s-1987-27924
日期:——
An attempt to confirm the structure proposed for phomazarin has been initiated by the synthesis of one of its degradation products. The methods chosen also resulted in the regiospecific elaboration of the B and C rings of the pigment and are applicable to eventual syntheses by convergent approaches.
Synthesis of functionalized phenolic derivatives via the benzannulation of dienylketenes formed by a thermal wolff rearrangement of α-diazo-β-keto compounds
Eleven conjugated dienyl α-diazo-β-keto derivatives were prepared from α,β-unsaturated carbonyl compounds. Their thermolysis induced a Wolff rearrangement generating an intermediate dienyl ketene whose isomer which has the required configuration of the internal double bond underwent a benzannulation thus forming the corresponding phenolic derivatives. When γ-substituted by a methoxy group both stereoisomers
The invention relates to pyrrolone compounds of the formula (I) wherein X, R
b
, R
c
, R
1
, R
2
and R
3
are as defined in the specification. Furthermore, the present invention relates to processes and intermediates for making compounds of formula (I), to herbicidal compositions comprising these compounds and to methods of using these compounds to control plant growth.
Stereocontrolled total synthesis of (+)-concanamycin F: the strategic use of boron-mediated aldol reactions of chiral ketones
作者:Ian Paterson、Victoria A. Steadman neé Doughty、Malcolm D. McLeod、Thomas Trieselmann
DOI:10.1016/j.tet.2011.09.012
日期:2011.12
cross-coupling reaction between the C1–C13 vinyl iodide and C14–C22 vinyl stannane fragments to assemble the (12E,14E)-diene, a modified Yamaguchi macrolactonisation delivered the requisite 18-membered macrocyclic core. This advanced intermediate was also obtained by an alternative sequence using an esterification step to connect the C1–C13 and C14–C22 fragments followed by a Pd-catalysed intramolecular