Nucleophilic 5-endo-trig cyclization of 3, 3-difluoroallylic ketone enolates: synthesis of 5-fluorinated 2-alkylidene-2, 3-dihydrofurans
T Fujita, K Sakoda, M Ikeda, M Hattori, J Ichikawa - Synlett, 2013 - thieme-connect.com
T Fujita, K Sakoda, M Ikeda, M Hattori, J Ichikawa
Synlett, 2013•thieme-connect.com… [ 10 ] Addressing the next challenge to the ‘disfavored’ process, we herein demonstrate
the 5-endo-trig cyclization with the metal enolates of 3,3-difluoroallylic ketones, which are
sp 2 atom-based ambident nucleophiles and rotationally restricted around the anionic
centers (Scheme [1], eq 3). This process efficiently provides 2-alkylidene-2,3-dihydrofurans[
11 ] by (i) constructing the heterocyclic ring and (ii) introducing a fluorine substituent and an
alkylidene group onto the prescribed ring carbon. … First, we sought bases suitable for the …
the 5-endo-trig cyclization with the metal enolates of 3,3-difluoroallylic ketones, which are
sp 2 atom-based ambident nucleophiles and rotationally restricted around the anionic
centers (Scheme [1], eq 3). This process efficiently provides 2-alkylidene-2,3-dihydrofurans[
11 ] by (i) constructing the heterocyclic ring and (ii) introducing a fluorine substituent and an
alkylidene group onto the prescribed ring carbon. … First, we sought bases suitable for the …
3,3-Difluoroallylic ketones readily undergo nucleophilic 5-endo-trig cyclization through their metal enolates to afford 5-fluorinated 2-alkylidene-2,3-dihydrofurans. O-Cyclization exclusively occurred via intramolecular substitution of the vinylic fluorines.
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