Beilstein J. Org. Chem.2018,14, 506–514, doi:10.3762/bjoc.14.36
preparation of oxazoles described in the literature. These include ring-closure reactions of diazocarbonyl compounds with amides or nitriles [16], α-haloketones and amides [17][18][19], cyanohydrins and aldehydes (Fischer synthesis) [20][21], or oxidative additions of α-methyleneketones to nitriles [22][23
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Graphical Abstract
Figure 1:
Examples of naturally occurring oxazoles (a); some drugs containing oxazole as the active moiety (b...
Beilstein J. Org. Chem.2015,11, 363–372, doi:10.3762/bjoc.11.42
dimerized to 30, the conversion of this olefin to 14 failed.
Keywords: α-methyleneketones; Cope rearrangement; cross-conjugation; indigo; McMurry coupling; Introduction
Cross-conjugated organic molecules are defined as unsaturated systems containing two π-electron systems (or lone pairs) that are in
-carbon analog of an indigoid dyestuff has failed so far. It is conceivable that unsubstituted α-methyleneketones such as 12 are too reactive to be isolated under the reaction conditions. On the other hand, if the methylene group is protected by two methyl groups, the corresponding ketone, 13, becomes
omitted.
From indigo to heteroindigo derivatives and all-carbon-indigo.
Attempts to prepare the α-methyleneketones 12 and 13.
Dimerization of 13 under McMurry conditions.
Dimerization of indan-1-one (18) by a stepwise approach.
Methylenation of 19 and bisalkylation of the product 23 with 1,2
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Graphical Abstract
Scheme 1:
From indigo to heteroindigo derivatives and all-carbon-indigo.