ISSN:
1434-4475
Keywords:
3-Chloro-2-ethoxycarbonyl crotonic aldehyde
;
2H-Benzopyrans
;
Pyrylium salts
;
Polymethin dyes
;
Grob-Fragmentation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary 3-Chloro-2-ethoxycarbonyl crotonic aldehydeC reacts with several 2-hydroxybenzene carbaldehydes and 2-hydroxy-naphthalene-1-carbaldehyde, respectively, to give 2-(ethoxycarbonyl-formyl-methylene)-2H-benzopyrans1a–h under mild conditions. With exception of1c and1d these compounds are mixtures ofE–Z isomers.1a–h easily undergo reactions, e.g. with aniline and derivatives to give2a–e, with various CH-acidic compounds to give3a–h and with 2-alkyl-4,6-diphenyl pyrylium salts to give4a–e. In the presence of alcoholic hydrochloric acid, compounds1 are converted into symmetrical 2,2′-benzopyrylotrimethine salts5a–e which exhibit longwave absorptions from 640–705 nm. These polymethine dyes with ester groups in the methine chain exhibit a remarkable thermal stability.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00811675
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