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Palladium‐katalysierte Ringschlußreaktionen zu Benzofuranen: ein neuer und effektiver Zugang zu Azacumöstrolderivaten
Author(s) -
Stadlbauer Wolfgang,
Laschober Rita,
Kappe Thomas
Publication year - 1990
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.1990199001101
Subject(s) - chemistry , palladium , ring (chemistry) , medicinal chemistry , aryl , catalysis , stereochemistry , organic chemistry , alkyl
Palladium‐Catalyzed Ring Closure Reactions to Benzofuranes: A New and Effective Approach to Azacoumestrols Azacoumestans (benzofuro[3,2‐ c ]quinolinones) 4 have been synthesized using the following three methods: ring closure of 3‐aryl‐4‐hydroxy‐2‐quinolones 3a – e by Pd‐catalyzed cyclodehydrogenation, ring closure of 3‐hydroxy‐3‐aryl‐2,4‐quinolinediones 5 by acid‐catalyzed cyclodehydratation, or ring closure of 4‐aryloxy‐3‐iodo‐quinolones 8 , which are obtained by rearrangement of iodonium ylides 7 , by palladium‐mediated cyclodehydrohalogenation. Only the latter reaction yielded the coumestrol analog dimethoxy derivatives 4c, d , which have been transformed into the hydroxy and acetoxy derivatives 9 , 10 .