A potentially general regiospecific synthesis of substituted quinones from dimethyl squarate
摘要:
A potentially general regiospecific synthesis of benzo- and naphthoquinones is described. This method starts with dimethyl squarate (1), which is converted to the cyclobutenone ketal 3 upon sequential treatment with an organolithium reagent and then BF3 etherate or TFAA in THF/methanol. Treatment of these with a second lithium reagent followed by hydrolysis gives the cyclobutenones 5. Addition of an alkynyl-, alkenyl- or aryllithium agent to 5 followed by hydrolysis of the ketal linkage gives the corresponding 4-alkynyl- 4-alkenyl- or 4-aryl-4-hydroxycyclobutenones 7-9, and these readily rearrange to the respective quinones or hydroquinones upon thermolysis in refluxing benzene. In a similar fashion, 15 was employed as a reagent to prepare mono- and disubstituted hydroquinones and quinones.
Photolysis of 4-substituted-4-hydroxy-3-cyclobuten-1-ones: a new route to butenolides from 4-hydroxycyclobutenones
作者:Steven T. Perri、Lafayette D. Foland、Harold W. Moore
DOI:10.1016/0040-4039(88)85284-5
日期:1988.1
ring closure to provide butenolide products. This transformation is envisaged to involve a stereoselective disrotatory electrocyclic ring opening to the corresponding conjugated ketene in which the C4 hydroxyl group rotates inward towards the ketene moiety. Intramolecular trapping of the ketene moiety with the proximal hydroxyl group results in the corresponding butenolide products.
An Efficient Flow-Photochemical Synthesis of 5<i>H</i>-Furanones Leads to an Understanding of Torquoselectivity in Cyclobutenone Rearrangements
作者:David C. Harrowven、Mubina Mohamed、Théo P. Gonçalves、Richard J. Whitby、David Bolien、Helen F. Sneddon
DOI:10.1002/anie.201200281
日期:2012.4.27
with the flow: 4‐Hydroxycyclobutenones were efficiently transformed into 5H‐furanones using an inexpensive flow‐photochemical setup. The results challenge the notion that this and the related thermochemical rearrangement display torquoselectivity in their electrocyclic opening to a vinylketene intermediate. Selectivity in the photochemicalrearrangement is due a dichotomous reactivity of the (E)‐ and
Reactivity of organo lithium reagents on dimethyl squarate : a 1,2-addition process leading to new 2-hydroxy-3,4 dimethoxy 3-cyclobutenone
作者:Jean Louis Kraus
DOI:10.1016/s0040-4039(00)94759-2
日期:1985.1
Lithiumreagents react with dimethylsquarate at the carbonyl group according to a 1,2-addition process, leading to new 2-hydroxy-3,4 dimethoxy-3 cyclobutenone.