Mechanistic Insights into the Reaction of N-Propargylated Pyrrole- and Indole-Carbaldehyde with Ammonia, Alkyl Amines, and Branched Amines: A Synthetic and Theoretical Investigation

Sari, Ozlem
Seybek, Ali Fatih
Kaya, Serap
Menges, Nurettin
The reaction of pyrrole- and indole-carbaldehydes having a propargyl group attached to the nitrogen atom with various amines was studied. The reaction with ammonia formed pyrrolo[1,2-a]pyrazine and pyrazino[1,2-a]indole while the reaction with alkylamines such as methyl, ethyl, hexyl, and benzylamines formed the corresponding pyrazinone derivatives. Unexpectedly, the reaction with allylamine and propargylamine formed pyrazine derivatives in which the allyl and propargyl groups were removed from the molecule. On the other hand, the reaction of N-propargylated pyrrole-carbaldehyde formed indolizine derivatives upon reaction with sterically bulky adamantyl- and tert-butylamines. To understand the main factors causing these differences in reactivity, the reaction mechanisms were studied by means of computational methods. Our calculations showed that bulky amines tend to attack the central carbon of allene formed by the isomerization of N-propargyl functionality, while the attack on the carbonyl carbon by aliphatic amines is more profound.


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3-Chloro-1,2,3,4-tetrahydro-1,4-epoxynaphthalen-2-yl)-3-hydroxy-5,5-dimethylcy-clohex- 2-en-1-one, synthesized by the reaction of oxabenzonorbornadiene with Mn(OAc)(3) and dimedone in the presence of HCl in acetic acid, was submitted to ring-opening reactions with BBr3 and H2SO4. Reaction with BBr3 yielded 2 products, a 5-membered ring and an 8-membered ring, with the former being the major product. However, the H2SO4-supported reaction exclusively formed an 8-membered ring. The mechanism of formation of th...
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Various ferrocene-based organosilanols have been synthesized in four steps starting from achiral ferrocene carboxylic acid. Applying these novel planar-chiral ferrocenes as catalysts in asymmetric phenyl transfer reactions to substituted benzaldehydes afforded products with high enantiomeric excesses. The best result (91% ee) was achieved in the addition to p-chlorobenzaldehyde with organosilanol 2b, which has a tert-butyl substituent on the oxazoline ring and an isopropyl group on the silanol fragment.
Excitation Localization/Delocalization Isomerism in a Strongly Coupled Covalent Dimer of 1,3-Diphenylisobenzofuran
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Two isomers of both the lowest excited singlet (S-1) and triplet (T-1) states of the directly para, para'-connected covalent dimer of the singlet-fission chromophore 1,3-diphenylisobenzofuran have been observed. In one isomer, excitation is delocalized over both halves of the dimer, and in the other, it is localized on one or the other half. For a covalent dimer in solution, such "excitation isomerism" is extremely rare. The vibrationally relaxed isomers do not interconvert, and their photophysical properti...
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Benzaldehyde lyase from the Pseudomonas fluorescens catalyzes the reaction of aromatic aldehydes with methoxy and dimethoxy acetaldehyde and furnishes (R)-2-hydroxy-3-methoxy-1-arylpropan-1-one and (R)-2-hydroxy-3,3-dimethoxy-1-arylpropan-1-one in high yields and enantiomeric excess via acyloin linkage. Aromatic aldehydes and benzoins are converted into enamine-carbanion-like intermediates prior to carboligation.
Chemoenzymatic synthesis of alpha(1)- and alpha-acetoxylated cyclic ketones
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alpha,beta-Unsaturated and saturated cyclic ketones were selectively oxidized at the alpha'- and alpha-positions using Mn(OAc)(3) and Pb(OAc)(4), respectively, resulting in high chemical yields. The resultant racemic alpha'- and alpha-acetoxylated substrates were resolved into corresponding enantiomerically enriched alpha'- and alpha-hydroxylated and acetoxylated compounds with 96-98% ee via PLE hydrolysis. The absolute configurations of alpha'-acetoxy-alpha,beta-unsaturated cyclic ketones were determined b...
Citation Formats
O. Sari, A. F. Seybek, S. Kaya, N. Menges, S. ERDEM, and M. BALCI, “Mechanistic Insights into the Reaction of N-Propargylated Pyrrole- and Indole-Carbaldehyde with Ammonia, Alkyl Amines, and Branched Amines: A Synthetic and Theoretical Investigation,” EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, pp. 5261–5274, 2019, Accessed: 00, 2020. [Online]. Available: