Succinic anhydride, tautomerism

Succinic anhydride (35, Z — O) can theoretically tautomerize to 36, but all the evidence indicates that it exists overwhelmingly as 35 for example, the infrared spectrum shows v C=0 bands. ... 

Another interesting facet of the question of tautomerism is that, under mild conditions for trimethylsilylation, succinic anhydride will enolize twice thus producing the bis(trimethylsilyi) derivative of furan-2,5-diol (80TL3423). Whether aromatization can be held to promote this synthetically important reaction remains unclear since butenolides and even butanolides react in a similar fashion (74JOC2558, 79BCJ1953). 

Methoxy- and 2-acetoxy-furans are available from 2,5-dimethoxy- and 2,5-diacetoxy-2,5-dihydro-furans (18.1.1.4) via acid-catalysed elimination. They undergo Diels-Alder cycloadditions the adducts can be further transformed into benzenoid compounds by acid-catalysed opening. 3,4-Dihydroxyfuran is undetectable in tautomeric equilibria between mono-enol and dicarbonyl forms the dimethyl ether behaves as a normal furan, undergoing easy a-electrophilic substitution, mono- or dilithiation at the a-position(s), and Diels-Alder cycloadditions. 2,5-Bis(trimethylsilyloxy)furan is synthesised from succinic anhydride it too undergoes Diels-Alder additions readily. Both furan-2- and -3-thiols can be obtained by reaction of lithiated furans with sulfur in each case the predominant tautomer is the thiol form. ... 

A useful class of activated acyl donors are enol esters, such as vinyl acetate or iso-propenyl acetate (Figure 5.4a). The product alcohol tautomerizes to a carbonyl compound, thereby driving the reaction toward product and eliminating possible inhibition by the released alcohol. Another activated acyl donor is succinic anhydride that yields a monosuccinate ester that can be easily separated from the starting alcohol by extraction with a basic aqueous phase. 

Acyl donors for hydrolase-catalyzed acylations. Reactive acyl donors like (a) vinyl acetate and (b) succinic anhydride react effectively irreversibly with alcohols. The tautomerization of the vinyl alcohol to the keto form makes the acylation favorable. These acyl donors are not suitable for amines because they react spontaneously. Simple esters like (c) triacetin are less expensive acyl donors. All three acetyl groups from triacetin can react. For alcohols, these simple ester acyl donors are reversible so are not suitable when kinetically controlled selectivity is important. Simple esters are good, effectively irreversible, acyl donors for amines. 

Guesten, H. Heinrich, G. Ache, H.J. (Inst. Radiochem., Kemforschungszent. Karlsruhe, 7500 Karlsruhe, Fed. Rep. Ger.). J. Photochem. 1985, 28 (3), 309-14 (Eng.). The use of photoacoustic spectroscopy in the study of the absorption spectra and thermal kinetics of photochromic reactions in the cryst. and adsorbed states was demonstrated in the following photochem. reactions E-a-(2,5-dimethyl-3-furylethylidene) (isopropylidene) succinic anhydride into 7,7 -dihydro-2,4,7,7 -pentamethylbenzo[b]furan-5,6-dicarboxylic anhydride, 2-(2 -dinitrobenzyl)pyridine into its blue tautomeric form, bis-(2-o-chlorophenyl-4,5-p-methoxyphenyl)diimidazolyl-l,l into its stable free imi-dazolyl radical and rrans-l,2-bis[quinolinyl-(2)]ethylidene dioxalate into its violene radical cation. By using the dnal illumination technique the absorption spectra and thermal lifetimes of short-lived photochromic species can be recorded by means of photoacoustic spectroscopy. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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