Pyridines. XIV¹ ‐Acylation de Pyridyl‐Lithioènamidines. Synthèse de Pyridyl‐N‐Acylènamidines et de Pyridylpyrimidones‐4

Abstract

The m i x t u r e P h L i : d i -o r t r i -m e t h y l p y r i d i n e 1:PhCN:RCOCl ( R = Me, Ph, EtO, Me N) or PhCOpMe (molar r a t i o 3:1:3:31 leads through t h e intermed'iates primary l i t h i o e n a m i n e s 3 an$ l i t h i o e n a m idines 4, t o a c y l a t e d products, N-acylenamines (enamides) 5, P-diketones and p=ketoesters 6, C-acylenamides 1, N-acylenamidines 8 and t h e i r c y c l i z a t i o n d e r i v a t i v e s , p y r i d y l hydroxypyrimidines lo ( y i e l d up t o 60%) and pyridyldihydropyrimidones 11 ( y i e l d up t o 10%). D i s t i l l a t i o n o f t h e crude e x t r a c t leads t o naphthyridones 12 ( y i e l d up t o 10%) which r e s u l t from t h e r m o c y c l i z a t i o n o f t h e enamides sf, a and If. Various by-products a r e i s o l a t e d such as N,N-dimethyl-N',N'-diphenylmethyleneurea r e s u l t i n g from N-lithiodiphenylketimine and phenacylpyridines 13. C r o t o n iz a t i o n and o x i d a t i o n o f t h e l a t t e r compounds lead t o t h e aza-analogues 3, 15 o f d i b e n z o y l s t i lbenes. RESUME ( p r o p o r t i o n m o l a i r e 3 : l :3:3) conduit par l ' i n t e h 5 d i a i r e des lithioenamines p r i m a i r e s 3 e t l i t h i o e n a m i d i n e s 4, aux p r o d u i t s acyles, N-acylhamines ( h a m i d e s 1 5, p-dicetones ou p-cetoesters 6, C-acylenamides L, N-acylenamidines 8 e t 1 l e u r s p r o d u i t s de c y c l i s a t i o n , p y r i d y l h y d r oxypyrirnidines (Rdt j u s q u ' a 60%) e t pyridyldihydropyrimidones 1_1 (Rdt j u s q u ' a 10%). La d i s t i ll a t i o n de l ' e x t r a i t b r u t l i v r e l e s naphtyridones 12 (Rdt j u s q u ' a 10%) qui r e s u l t e n t de l a t h e rm o c y c l i s a t i o n des enamides 5f, a e t Lf. Divers sous-produits sont i s o l e s , t e l l e s l a N,N-dime-thy1 N',N'-diphenylmethyleneuree provenant de l a N -l i t h i o d i p h e n y l c e t i m i n e e t l e s phenacylpyri-&nes 13. C r o t o n i s a t i o n e t oxydation de ces dernieres conduisent aux analogues azotes 14, 15 de d i benzoyl s t i 1 benes. Le melange P h L i : d iou t r i -m e t h y l p y r i d i n e 1:PhCN:RCOCl ( R = Me, Ph, E t O , Me2N) ou PhCD2Me

Synthesis of a 7-Azaindole by Chichibabin Cyclization: Reversible Base-Mediated Dimerization of 3-Picolines

“…This loss of PhCN was traced to the condensation of the remaining LDA (0.5–1.5 equiv; not shown) to form amidinolithium 6 as the first step of a cascade of reactions leading to PhCN trimer 15 (Scheme 4). 31–33 Indeed, warming a mixture of 6 and PhCN to 0 °C affords an intensely purple solution (appearing black), which affords PhCN-derived trimer 15 in 83% yield. Base-mediated trimerizations of arylnitriles have been reported previously 31,32…”

“…31–33 Indeed, warming a mixture of 6 and PhCN to 0 °C affords an intensely purple solution (appearing black), which affords PhCN-derived trimer 15 in 83% yield. Base-mediated trimerizations of arylnitriles have been reported previously 31,32…”

“…If adduct 6 stands for several hours or is warmed above −40 °C, further oligomerization occurs, eventually affording trimer 15 (Scheme 4). 31,32 Provided the cascade leading to 15 is not allowed to occur, formation of amidinolithium 6 does not preclude formation of azaindole 2 .…”

“…The off-white solid was recrystallized from neat ethyl acetate. Known31 trimer 15 (340 mg, 1.10 mmol) was isolated as a white solid in 83% yield. 1 H NMR (DMSO- d 6 ) δ, 8.74–8.78 (6H, m).…”