Synthesis of highly functionalized 3,4-cyclohexane-annelated coumarins
作者:Chao-Yue Chen、Xiao-Mei Zhang、Jian-Jun Shi、Jie He
DOI:10.1007/s11164-013-1212-2
日期:2015.2
Efficient synthetic access to highly functionalized 3,4-cyclohexane-annelated coumarins has been achieved by combining two methods. First, the important intermediates multisubstituted cyclic β-keto esters were prepared conveniently by condensing a variety of benzaldehydes with ethyl acetoacetate. A series of highly functionalized 3,4-cyclohexane-annelated coumarins were then synthesized by Amberlyst-15-catalyzed
Über Steroide. 100. Mitteilung. Zur Biosynthese der Steroide
作者:K. Miescher、P. Wieland
DOI:10.1002/hlca.19500330654
日期:——
Mol NaOH und geringer Mengen sekundärer Base in verdünnter, wässeriger Lösung unter Bildung des Hagemann-Esters (IX) kondensieren. Diese Tatsache dient als Ausgangspunkt einer Hypothese über die Biosyntheseder Steroide, wonach als wesentlichste Aufbauelemente Acetessigsäure und Formaldehyd anzusehen wären. Es ergeben sich damit enge Beziehungen im natürlichen Aufbau verschiedenartigster Naturstoffe.
In the presence of trifluoroacetic acid and methanesulfonic acid (MSA), a series of monohydric and polyhydric phenols readily undergo a domino Pechmann-dehydration reaction with various 4-hydroxy-6-oxocyclohexane-1,3-dicarboxylates to give 7,8-dihydro-6H-dibenzo[b,d]pyran-6-ones. Subsequent dehydrogenation of the 7,8-dihydro-6H-dibenzo[b,d]pyran-6-ones was performed expediently with DBU/BrCCl3 to give various 6H-dibenzo[b,d]pyran-6-one derivatives. This strategy has the advantages of inexpensive and easily available raw materials, metal-free procedure, mild reaction conditions, good compatibility with various functional groups, and satisfactory yields.
Rabe; Pollock, Chemische Berichte, 1912, vol. 45, p. 2926