The first example of 2,2-dilithiocyanocyclopropanes: generation from 2-bromo-2-sulfinylcyanocyclopropanes with tert-butyllithium, property, and a synthesis of fully substituted cyanocyclopropanes
作者:Iori Fukushima、Youhei Gouda、Tsuyoshi Satoh
DOI:10.1016/j.tetlet.2006.12.148
日期:2007.3
through concomitant sulfoxide–lithium and bromine–lithium exchange reactions. The gem-dianions were found to be stable at −78 °C for at least 30 min. Reaction of the gem-dianions with electrophiles gave fully substituted cyanocyclopropanes in moderate yields.
On the other hand, the addition reactions of 1-chlorovinyl p-tolyl sulfoxides derived from aldehydes with lithium acetylides directly gave conjugated enynes bearing a p-tolyl sulfinyl group at the 1-position through the 1,2-carbon–hydrogen insertion (1,2-CH insertion) reaction of the generated lithium carbenoid intermediates. These procedures provide a good way for the synthesis of multi-substituted
enolate of carboxylic acid tert-butyl esters or N,N-dimethylacetamide gave adducts in high yields. The adducts were treated with ether solution of isopropylmagnesiumchloride in dry toluene to give bicyclo[n.1.0]alkane derivatives having tert-butyl carboxylate or acetamide moiety on the bridgehead carbon in high to quantitative yields via magnesium carbenoid 1,3-CH insertion reaction. The 1,3-CH insertion
A new synthesis of β,γ-unsaturated esters and allenic esters with construction of a carbon–carbon bond between α- and β-positions by the reaction of magnesium alkylidene carbenoids with lithium ester enolates
Treatment of lithium ester enolates with magnesium alkylidene carbenoids, generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride via the sulfoxide–magnesium exchange reaction, gave β,γ-unsaturated esters in moderate to good yields. When this reaction was conducted with the lithium ester enolates of α-chlorocarboxylic acid esters, allenic esters were obtained. This procedure
Alkenylation of thiophenes and furans at the 2-position and a synthesis of allenes conjugated with α,β-unsaturated ester with magnesium alkylidene carbenoids
to afford thiophenes and furans bearing a fully substituted alkene at the 2-position. Treatment of the magnesium alkylidene carbenoids with 2-lithio-5-methoxyfuran afforded allenes conjugated with α,β-unsaturated methyl ester in moderate yields. These procedures offer a new and versatile one-pot synthesis of 2-alkenylthiophenes, 2-alkenylfurans, and allenes conjugated with α,β-unsaturated methyl ester