ABSTRACT
4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4'-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior.
Subject(s)
Diazonium Compounds/chemistry , Phenols/chemical synthesis , Salts/chemistry , Stilbenes/chemical synthesis , Styrenes/chemistry , Catalysis , Palladium/chemistry , Phenols/chemistry , Stilbenes/chemistryABSTRACT
The Suzuki-Miyaura coupling of phenol diazonium salts and aryl trifluoroborates yields 4-hydroxybiaryls in a protecting group-free synthesis.
Subject(s)
Diazonium Compounds/chemistry , Phenol/chemistry , Benzoquinones/chemistry , Molecular StructureABSTRACT
The first total synthesis of the natural product (3S,7R)-5,6-dehydro-de-O-methyl centrolobine and various analogues is reported, using a highly regio- and diastereoselective Mizoroki-Heck reaction of phenol diazonium salts and enantiopure dihydropyrans. The assigned relative configuration was confirmed by single-crystal X-ray structure analysis, but a revision of the absolute configuration is proposed based on polarimetric measurement.
Subject(s)
Diarylheptanoids/chemical synthesis , Diazonium Compounds/chemistry , Palladium/chemistry , Phenol/chemistry , Biological Products/chemical synthesis , Biological Products/chemistry , Catalysis , Diarylheptanoids/chemistry , Ethers, Cyclic/chemistry , Pyrans/chemical synthesis , Pyrans/chemistry , Stereoisomerism , Substrate SpecificityABSTRACT
Arene diazonium tetrafluoroborates can be synthesized from aromatic acetamides via a sequence of deacetylation, diazotation and precipitation, induced by anion exchange. The reaction is conducted as a convenient one-flask transformation with consecutive addition of the appropriate reagents. Exchange of solvents or removal of byproducts prior to isolation of the product is not required. The arene diazonium salts are isolated from the reaction mixture by simple filtration. Two complementary protocols are presented, and the utility of the reaction is exemplified for a synthesis of the diarylheptanoid natural product de-O-methyl centrolobine.
Subject(s)
Acetaminophen/chemistry , Borates/chemistry , Diazonium Compounds/chemical synthesis , Acetylation , Biological Products/chemical synthesis , Biological Products/chemistry , Diazonium Compounds/chemistry , Pyrans/chemical synthesis , Pyrans/chemistry , Water/chemistryABSTRACT
All stereoisomers of the natural product centrolobine are selectively synthesized, by starting from a common precursor. Key steps are an enantioselective allylation with enantiomerically pure allylsilanes, a tandem ring-closing metathesis-isomerization reaction, and a Heck reaction by using an arene diazonium salt. By choosing appropriate conditions for the final deprotection step, either the cis-configured centrolobines or their epimers are selectively obtained.
