691-45-2

Upstream product

• 5394-63-8 2,2,6-trimethyl-4H-1,3-dioxin-4-one 
• 171085-78-2 Ethoxyvinylketene 
• 14369-81-4 ethyl 2,3-butadienoate 
• 4683-54-9 3-ethoxy-2-cyclobuten-1-one 

Downstream Products

• 115026-44-3 3-Acetyl-1-[bis-(4-methoxy-phenyl)-methyl]-4-[(S)-1-(1-ethoxy-ethoxy)-ethyl]-azetidin-2-one 
• 115026-43-2 (3S,4S)-3-acetyl-4-<(S)-1-benzyloxyethyl>-1-(di-p-anisylmethyl)-2-azetidinone 
• 115075-45-1 (3R,4R)-3-acetyl-4-<(S)-1-benzyloxyethyl>-1-(di-p-anisylmethyl)-2-azetidinone 
• 115026-43-2 (3R,4R)-3-Acetyl-4-((R)-1-benzyloxy-ethyl)-1-[bis-(4-methoxy-phenyl)-methyl]-azetidin-2-one 
• 54527-68-3 2-chloroethyl acetoacetate 
• 74-99-7 prop-1-yne 
• 1137557-59-5 N-methyl-3-oxo-N-(2,3,4-trimethoxyphenyl)butanamide 
• 1137557-63-1 N-methyl-3-oxo-N-(2,4,5-trimethoxyphenyl)butanamide 
• 1137557-57-3 3-oxo-N-(2,3,4-trimethoxyphenyl)butanamide 
• 100390-66-7 N-(2-methoxyphenyl)-N-methyl-3-oxobutanamide 
• 365242-41-7 N-(2,3-dimethoxyphenyl)-3-oxobutanamide 
• 131451-77-9 N-(2,5-dimethoxyphenyl)-N-methyl-3-oxobutanamide 
• 152532-10-0 3-oxo-N-(2,4,5-trimethoxyphenyl)butanamide 
• 1137557-53-9 N-(2,4-dimethoxyphenyl)-N-methyl-3-oxobutanamide 

Relevant academic research and scientific papers

Retro-Ene Reactions in Acylallene Derivatives

Allenic esters and amides 4 undergo a retro-ene reaction to vinylketene (6) and an aldehyde or imine (5) under the conditions of flash vacuum thermolysis (FVT). The same products are obtained by FVT of cyclobutenones 7 via electrocyclic ring opening to alkoxy- or aminovinylketenes 3 and 1,3-rearrangement of ketenes 3 to allenes 4. All the intermediates and products were characterized by matrix isolation IR spectroscopy, and in the case of 4c the reaction was also monitored by online mass spectrometry. A lower temperature for the retro-ene reaction of 4c, eliminating an imine, than for 4a, eliminating formaldehyde, is in agreement with a lower calculated activation barrier (167 and 181 kJ mol-1, respectively, at the G2(MP2,SVP) level of theory). The allenic amide 11 undergoes an analogous retro-ene reaction to the (unobserved) vinylketene 13, the latter isomerizing to cyclohexenylacrolein 16 in a 1,5-H shift (calculated barrier 125 kJ mol-1; G2 (MP2, SVP)).

Chemoselectivity in the Reactions of Acetylketene and Acetimidoylketene: Confirmation of Theoretical Predictions

Acetylketene (1) was generated by flash pyrolysis of 2,2,6-trimethyl-4H-1,3-dioxin-4-one (6). The selectivities of 1 toward a number of representative functional groups were measured for the first time in a series of competitive trapping reactions. The trend in reactivities toward 1 follows the general order amines > alcohols aldehydes ≈ ketones and can be rationalized by considering both the nucleophilicity and the electrophilicity of the reacting species. Alcohols show significant selectivity based on steric hindrance, with MeOH ≈ 1° > 2° > 3°. These selectivities are consistent with the activation energies and the pseudopericyclic transition structure previously calculated for the addition of water to formylketene. The results, presented here, of ab initio transition structure calculations for the addition of ammonia to formylketene are qualitatively consistent with the experimental trends as well. N-Propylacetacetimidoylketene (2) was generated by the solution pyrolysis of tert-butyl N-propyl-3-amino-2-butenoate (9a) and showed similar selectivity toward alcohols as opposed to ketones and similar steric discrimination toward alcohols. This is again in agreement with previous ab initio calculations. Taken together, these experimental trends in the reactivities of both 1 and 2 toward a variety of reagents provide strong, although indirect support for the planar, pseudopericyclic transition structures for these reactions which are predicted by ab initio calculations.

The vinylketene-acylallene rearrangement: Theory and experiment

Alkoxyviniyketenes 4 are generated by flash vacuum thermolysis (FVT) or photolysis of 3-alkoxycyclobutenones 3. The thermal interconversion of 4 and allene carboxylic acid esters 5 under FVT conditions is demonstrated by Ar matrix FTIR spectroscopy. In addition, ethoxyvinylketene 4b undergoes thermal elimination of ethene with formation of s-cis-and s-trans-acetylketene (8). An analogous aminovinylketene-to-allenecarboxymide conversion is observed on FVT of 3-dimethylaminocyclobutenone 3e. A facile 1,3-chlorine migration in 2,3-butadienoyl chloride (5d) is also reported. Consistent with the experimental observations, 1,3-methoxy, 1,3-chloro, and 1,3-dimethylamino migrations in vinylketene are calculated (G2(MP2,SVP) level) to have moderate barriers of 169, 157, and 129 kJmol-1, respectively, significantly less than the corresponding 1,3-H shift barrier (273 kJ mol-1). The stabilization of the four-center transition structures is rationalized in terms of the donor acceptor interaction between the lone pair electrons of the migrating donor substituent and the vacant central carbon p-orbital of the ketene LUMO. The predicted migratory aptitude in the series of substituted vinylketenes. R-C(=CH2)-CH=C=O, is in the order N(CH3)2>SCH3>SH>Cl>NH2>OCH3>OH>F>H>CH3, and correlates well with the electron-donating ability of the R group.

Direct Observation of α-Oxo Ketenes Formed from 1,3-Dioxin-4-ones and the Enols of β-Keto Esters

The enol forms of β-keto esters thermolyze to alcohols and α-oxo ketenes, which are characterized by low-temperature IR spectroscopy and on warming regenerate the β-hydroxy-α,β-unsaturated esters. The matrix isolated s-Z and s-E forms of α-oxo ketenes are characterized and photochemically converted into other conformers or sites.Matrix photolysis of 2,2,6-trimethyl-1,3-dioxin-4-one gives the s-Z acetylketene initially. α-Oxo ketenes polymerize in the cold and dimerize only at elevated temperatures.