Aldol condensations with butanone

Abstract

A new method for the aldol condensation of citral with butanone is described by which the condensation takes place mainly at the methylenc group of the ketone. The mechanism of the reaction is discussed.The condensation of an aldehyde with butanone may take place theoretically in two different ways, i.e. at the methylene group ( I ) or at the methyl 'group (11) of bhe ketone.The literature data show that the ratio between the amounts of the two compounds present in the condensation product is influenced by several factors.Harries and Miifler 3 ) demonstrated the influence of the catalyst; the condensation of benzaldehyde with butanone takes place practically exclusively at the methylene group when the mixture is saturated with hydrogen chloride.Whereas all available literature data 4 ) 6 ) seem to indicate that the I ) The method described in this gaper is the subject of patent applications (e.8.2 ) This paper was presented before the VIIIth Congress0 nazlonale di chimica.

Intraparticle Diffusional versus Site Effects on Reaction Pathways in Liquid‐Phase Cross Aldol Reactions

“…Independent of the conditions, this catalyst promoted Pathway A, consistent with the regioselectivity reported in the literature. Acid catalysts are known to lead to reaction at the methylene group and formation of the branched addition product . As can be seen in Table , Entries 1 to 4, the selectivity to the addition product decreased with conversion whereas the selectivity to the condensation product increased, as is expected for an intermediate product in a series reaction.…”

“…Pre‐enolization is the most commonly applied method . Variation of the catalyst can also be successful; for example, acids activate hydrogen in the ‐CH 2 ‐ group in butanone whereas bases activate the ‐CH 3 group . Solvents have been reported to significantly affect selectivity in some cases, for example, the enantioselectivity in the Mukayama aldol reaction or the diastereoselectivity in the reaction of tert ‐butyl acetate and 2‐phenyl propanal .…”

Optimization of the Pd-Catalyzed Alkylation of the Fermentation-Derived Oxygenates Acetone and Butanol toward Sustainable Aviation Fuel (SAF) Intermediates

“…No water was added as cosolvent in the present work, where the solvent was a reactant as well, thus making the final C higher than compared to the work by Xie et al Consequently, mass transfer limitations may also be the reason why higher activity (TON) was obtained in the present study with lower C. As for the B, the associated increase in double alkylation selectivity toward C11 was also seen in previous related studies, 18,29,30 as basicity promotes the alkylation to occur with the less reactive methyl group of the ketone. 41 Moreover, as aldol condensation is base-catalyzed, 7 higher B resulted in an increased overall alkylation efficiency. On the other hand, T was not relevant for C11 selectivity as a standalone factor but only when considering its combined effect with C.…”

Catalytic production of long-chain hydrocarbons suitable for jet-fuel use from fermentation-derived oxygenates

“…45 However, this might be challenging to achieve as aldol condensation in unsymmetric ketones occurs differently depending on the reaction conditions: acidic conditions promote alkylation at the α-carbon of the longer alkyl group while alkaline conditions promote reaction on the methyl group. 46 In the depicted example, one molecule of acetone is bonded with two molecules of butanol. The product mixture obtained from ABE fermentation therefore provides a coupled functionality where several different molecules can be obtained depending on the combination between them, as shown on Scheme 3.…”