Beilstein J. Org. Chem.2009,5, No. 32, doi:10.3762/bjoc.5.32
. (a) arylation at C-4 followed by alkynylation at C-2 or (b) alkynylation at C-2 followed by arylation at C-4. Methodologies based on strategy ‘a’ have been reported earlier. For example, Sonogashira coupling of a terminalalkyne with 2-chloro-4-aryl substituted quinoline [3] in the presence of (PPh3
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Graphical Abstract
Figure 1:
2-Alkynyl-4-aryl pyridine and its benzo derivative.
Beilstein J. Org. Chem.2007,3, No. 21, doi:10.1186/1860-5397-3-21
low yields could be improved by optimizing the reaction conditions and finding a better way to add the second arm to the acetal, such as a catalytic method, avoiding the need for the bromosilane intermediate. This reaction was repeated using 3-butyn-1-ol to yield the isomeric, terminalalkyne product
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Graphical Abstract
Scheme 1:
Saigo's cycloisomerisation reaction under Pauson-Khand conditions.