Abstract
A series of new 2,3-disubstituted-3,4-dihydro-2H-1,3-benzoxazines were prepared in moderate to excellent yields by aza-acetalizations of aromatic aldehydes with 2-(N-substituted aminomethyl)phenols in the presence of TMSCl. Their structures were confirmed by IR, 1H-NMR, 13C-NMR, MS and elemental analysis. The fungicidal activities of the target compounds were preliminarily evaluated, and some compounds exhibited good activity against Rhizoctonia solani.
Highlights
A series of new 2,3-disubstituted-3,4-dihydro-2H-1,3-benzoxazines were prepared in moderate to excellent yields by aza-acetalizations of aromatic aldehydes with
We present the synthesis of a series of novel 2-aryl-3-alkyl-3,4-dihydro-2H-1,3-benzoxazines, as a continuation of our ongoing project aimed at searching for novel biological active nitrogen and oxygen linked heterocyclic compounds, by reactions of aromatic aldehydes with 2-(N-substituted aminomethyl)-phenols in the presence of chlorotrimethylsilane (TMSCl) [22,23,24,25], and report their fungicidal activities
The reaction of fluorobenzaldehyde (5d) with 2-((4-methylphenyl)aminomethyl)phenol (4a) which was prepared in high yield by reaction of salicylaldehyde and p-toluidine followed by reduction with NaBH4 in a one-pot process [21,26,27] was chosen as model reaction for the synthesis of the title compounds 6a–n
Summary
A series of new 2,3-disubstituted-3,4-dihydro-2H-1,3-benzoxazines were prepared in moderate to excellent yields by aza-acetalizations of aromatic aldehydes with. 2-(alkenyloxy)benzylamines which involve an allylic cleavage followed by regioselective carbonylation at the internal carbon atom have been developed as a new way to generate 3,4-dihydro-1,3benzoxazines [19,20] Despite these advances, the synthesis of novel 3,4-dihydro-2H-1,3-benzoxazines and the search for more efficient routes for drug discovery and medicinal chemistry are still highly desirable. In our previous paper [21], a new method by SnCl4-mediated aza-acetalization reactions of aromatic aldehydes with 2-arylaminomethyl phenols to synthesize substituted 3,4-dihydro-2H-1,3benzoxazines was developed and the compounds showed good fungicidal activity. We present the synthesis of a series of novel 2-aryl-3-alkyl-3,4-dihydro-2H-1,3-benzoxazines, as a continuation of our ongoing project aimed at searching for novel biological active nitrogen and oxygen linked heterocyclic compounds, by reactions of aromatic aldehydes with 2-(N-substituted aminomethyl)-phenols in the presence of chlorotrimethylsilane (TMSCl) [22,23,24,25], and report their fungicidal activities
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