- Preparation of New Nitrogen-Bridged Heterocycles. 42.1 Synthesis and the Reaction of Pyridinium N-Ylides Using Bifunctional Ethyl Thiocyanatoacetates
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Various pyridinium (monosubstituted methylide)s were smoothly attacked to the cyano group in ethyl thiocyanatoacetate or ethyl 2-thiocyanatopropionate to afford the corresponding pyridinium (substituted cyanomethylide)s in low-to-moderate yields, while pyridinium (unsubstituted amidate)s reacted with the ester carbonyl group in the same reagents to give pyridinium (thiocyanatoaceto)- or (2-thiocyanatopropiono)amidates in considerable yields. The 1,3-dipolar cycloadditions of some pyridinium (unsymmetrically substituted cyanomethylide)s with dimethyl acetylenedicarboxylate (DMAD) in various solvents afforded only dimethyl 3-cyanoindolizine-1,2-dicarboxylate, except a few examples. On the other hand, the treatment of pyridinium (thiocyanatoaceto)- or (2-thiocyanatopropiono)amidates with a strong base, such as potassium t-butoxide, gave new bicyclic mesoionic compounds, N-[2-(1,3,4-thiadiazolo(3,2-a]pyridinio)]acetamidate derivatives, in moderate yields. The intermediacy of N-[1-(2-thiocyanatopyridinio)]acetamidates in the formation reactions of the latter compounds was also proven by independent syntheses.
- Kakehi, Akikazu,Ito, Suketaka,Hashimoto, Yasunobu
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p. 1769 - 1776
(2007/10/03)
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- Substitution of 2-(Sulfonyloxy)carboxylates with Oxygene and Sulfur Nucleophiles without Racemization
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The ethyl 2-(sulfonyloxy)propionates (S)-1a-c react with phenolates formed from 2 and with carboxylates 8 to give the respective 2-(aryloxy)- (R)-3 and 2-(acyloxy)propionates (R)-9 with inversion of configuration.Due to the high leaving tendency of the triflate group, (S)-1a generally give higher yields of substitution products under milder conditions than the corresponding mesylate (S)-1b and tosylate (S)-1c.In the case of the reaction of malic and succinic acid derivatives only the triflate (S)-10a is converted to the acyloxy compounds (R)-12 with carboxylates 8 atlow temperature (-45 deg C); with the mesylates 10b and the bromide 10d only elimination is observed.Mercaptides and thiophenolates formed from 17 react with (S)-1a-c analogously.With potassium thiocyanate 1a,b react almost exclusively to give the thiocyanate 19; only traces of the corresponding isothiocyanate 20 are obtained.
- Burkard, Ulrike,Effenberger, Franz
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p. 1594 - 1612
(2016/06/15)
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