Beilstein J. Org. Chem.2021,17, 1181–1312, doi:10.3762/bjoc.17.90
to fragrance chemists. This section investigates the aldol reaction as this is a vital C–C and C=C bond forming tool within this class of reactions. Other sequences such as the Knoevenagel and Darzenscondensation, however, will also be considered as part of the evaluation.
The condensation of
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Graphical Abstract
Figure 1:
Representative shares of the global F&F market (2018) segmented on their applications [1].
Beilstein J. Org. Chem.2016,12, 531–536, doi:10.3762/bjoc.12.52
cyclohexenones 13/36 in the presence of LiOt-Bu to give brominated anthraquinones 14/38 in good yields. Darzenscondensation of 30 was shown to give chain-elongated anthraquinone 32. Alkaline hydrolysis of 38 furnished 39 representing desulfoproisocrinin F.
Keywords: brominated anthraquinones; Darzens
carboxyaldehyde 15. Employment of a Darzenscondensation followed by bromination was considered for further elaboration of 15 to 16.
For the synthesis of key synthon 12 (Scheme 2), we started from cyclohexenone 19, which was prepared by base-catalyzed condensation of methyl acetoacetate with methyl crotonate [24
.
Initially proposed synthetic scheme for proisocrinins 6–11.
Synthesis of cyanophthalide 12.
Synthesis of cyclohexenone 13.
Darzenscondensation route to proisocrinins.
Synthesis of cyclohexenone 36.
Synthesis of the proisocrinin core structure.
Supporting Information
Supporting Information File 2: Detailed