4-Picoline derivatives are converted to the corresponding aryl picolyl sulfones upon treatment with aryl sulfonyl chlorides and Et 3 N in the presence of catalytic DMAP. The reaction proceeds smoothly for a variety of alkyl and aryl picolines using a range of aryl sulfonyl chlorides. The reaction is believed to involve N-sulfonyl 4alkylidene dihydropyridine intermediates and results in formal sulfonylation of unactivated picolyl C−H bonds.
4-Alkylpyridines are converted to conjugated 1,1-disubstituted alkenyl pyridines (vinyl pyridines) upon treatment with excess ethyl chloroformate, triethylamine, and Eschenmoser’s salt. The reaction proceeds under mild conditions via alkylidene dihydropyridine intermediates
Aldehyde-derived
imidazolidines participate as hydride donors in
intramolecular reductive Heck-type reactions.
N
,
N
′-Diphenylimidazolidines prepared from
ortho
-alkynyl benzaldehydes underwent regio- and stereoselective palladium-catalyzed
hydroarylation followed by formal 1,5-hydride transfer and reductive
elimination to afford substituted alkenes and imidazolium moieties,
the latter conveniently converted in situ to ring-opened benzanilides
to simplify product isolation. Internal alkynes were converted to
trisubstituted alkenes via a
syn
hydroarylation process,
while a terminal alkyne was converted to a
cis
alkene
via a formal
trans
hydroarylation reaction. Benzanilide
products could be converted to carboxylic acid derivatives under basic
conditions, resulting in the net conversion of alkynyl aldehydes to
alkenyl carboxylic acids. A styrene derivative with an attached
N
,
N
′-dimethylbenzimidazoline hydride
donor was also found to undergo an analogous hydroarylation/benzimidazoline
oxidation to give a diarylethane product.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.