Trimerization of 3-Trimethylsilyl-2-propyn-1-al into 4-Trimethylsilylethynyl-4H-pyran-3,5-dicarbaldehyde

Abstract

Dedicated to Academician of the Russian Academy of Sciences N.S.Zefirov on occasion of his70 th anniversary 0H 6L 2 0H 6L +2 2 2+ 2 2 2+ 2+ 6L0H 2 +2 2+ 6L0H 2 2 2 6L0H , ,, $ , 2 ,,, + 2 '$%&2 + 2 0H 6L2+ B ,, B + 2 B + 2 % &We recently showed the possibility to perform onepot direct conversion of organoelemental a-acetylene alcohols R 3 MCºCCH 2 OH into 1,3-enynes R 3 MCºCCH=CR 1 R 2 under the action of pyridinium chlorochromate on Al 2 O 3 in the presence of CH-acids R 1 CH 2 R 2 assisted by a microwave irradiation [1]. The reaction occurred as a tandem process involving the alcohol oxidation into the corresponding aldehyde followed by the Knoevenagel condensation with the CHacid. The 3-trimethylsilyl-2-propyn-1-al is also known to react with nitromethane in the presence of catalytic amount of piperidine to afford a Knoevenagel adduct Me 3 SiCºCCH=CHNO 2 in 42% yield [2].However in reaction of 3-trimethylsilyl-2-propyn-1-al (I) with nitromethane in acetonitrile in the presence of 5 mol% of diazabicyclooctane (DABCO) at room temperature instead of the expected nitroenine we isolated 4-trimethylsilylethynyl-4H-pyran-3,5-dicarbaldehyde (III). The reaction proceeded for 48 h and afforded the product in high yield (98% by 1 H NMR data). It was established that the nitromethane was not involved into the formation process of heterocycle III since in its absence under the same conditions (25°C, 5 mol% DABCO, MeCN, 48 h) diformylpyran III also was the only reaction product. Compound III was isolated by column chromatography on SiO 2 , its structure was proved by NMR ( 1 H, 13 C, HSQC, HMBC), IR spectroscopy, and mass spectrometry, the composition was confirmed by elemental analysis.We believe that the reaction starts by a nucleophilic addition of water to the triple bond of propynal I affording malodianaldehyde II which further reacts as a C-nucleophile with the carbonyl group of propynal I to furnish aldol B. Aldol B is able to condense further with the

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

“…leading to the cascade assembly of polyfunctional nitrogen-and oxygen-containing heterocycles -2H-1,2'-bipyridine 166, imidazo[1,2-a]pyridine 167, and 4H-pyran 168[403] -from elementcontaining propynals and 2-pyridineamine or water were discovered (A. S. Medvedeva et al)[401][402][403]. Imidazo[1,2-a]pyridine 169 is formed during the acid-catalyzed reaction of 2-pyridineamine with phenylpropynal.…”

Silicon- and germanium-substituted propynals as ambident electrophiles for the design of new heterocycles and polyfunctional acetylenes

“…(45) in 98% yield. 177 We suggest (Scheme 23) that the reaction begins with nucleophilic addition of water to the triple bond of propynal 2a and formation of malondialdehyde (46) Similar trimerization of unsubstituted propynal 2i is described in papers, 179,180 however, the authors do not suggest a scheme for its formation.…”

10.1007/s11178-008-1020-0

“…3-Trimethylsilylprop-2-ynal underwent quantitative trimerization to 4-trimethylsilylethynyl-4H-pyran-3,5-dicarbaldehyde, catalyzed by 5 mol % of diazabicyclooctane (DABCO) in acetonitrile [3]. For example, 3-trimethylsilylprop-2-ynal (I) reacted with pyridin-2-amine (II) in the presence of 5 mol % of p-toluenesulfonic acid or hydrochloric acid under microwave irradiation (MW, 6 min, 700 W), as well as under usual conditions (25°C, 7 days), to give 75% of N-(pyridin-2-yl)-2-(trimethylsilylethynyl)-1,2dihydropyridine-3,5-dicarbaldehyde [1].…”