| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 885.96 KB | Adobe PDF |
Advisor(s)
Abstract(s)
The conjugate addition of carbon nucleophiles to electron deficient alkenes is an important method
for carbon-carbon bond formation [1]. Generally, 1,4-conjugate addition reactions are more
developed than its analogous 1,6- or 1,8-additions, mainly due to the presence of several
electrophilic sites in extended conjugated systems as well as the inherent difficulties in controlling
the regioselectivity (1,4- vs. 1,6- vs. 1,8-addition) [1].
In this work, we provide new experimental and computational insights about the reactivity of the
3,2:α,β:γ,δ-triunsaturated system of the 2-[(1E,3E)-4-arylbuta-1,3-dien-1-yl]-4H-chromen-4-ones 1
in conjugate addition reactions with carbon nucleophiles (Figure 1). The 1,6-conjugate addition of
nitromethane to chromones 1 afforded the corresponding β-(nitromethyl)chromones 2 as major
products. (E)-5′-(Nitromethyl)-3′-styryl-[1,1′-biphenyl]-2-ols 3 and 3′-aryl-2′-nitro-5′-
(nitromethyl)spiro[chromane-2,1′-cyclohexan]-4-ones 4 were also isolated as minor products,
which result from tandem reactions [2].
The nucleophile scope (malononitrile, acetylacetone, diethyl malonate and ethyl cyanoacetate) of
this reaction was also assessed and gave, in all cases, the expected 1,6-addition products 5 as major
products. Computational calculations showed that the reaction is probably kinetically driven
towards 1,6-addition. The further functionalization of some adducts allowed the preparation of
new nitrogen-containing heterocyclic compounds, such as pyrazole derivative 6 and
styrylpyrrolidines 7 [2].
Description
Keywords
Pedagogical Context
Citation
Albuquerque, Hélio; Santos, Clementina M.M.; Balanay, Mannix P.; Cavaleiro, José; Silva, Artur (2017). Conjugate additions of carbon nucleophiles to chromones substituted with extended π-systems at C-2. In XXIII Encontro Galelo Portugués de Química. Ferrol. ISBN 978-84-697-7356-7