43059-50-3Relevant academic research and scientific papers
Synthesis of methyl 3-bromomethylbut-3-enoate and its reactions with aldehydes and tributylchlorostannane in the presence of zinc
Mineeva,Kulinkovich
experimental part, p. 1261 - 1266 (2009/07/17)
Methyl 3-bromomethylbut-3-enoate smoothly reacted with prenal, β-ionylideneacetaldehyde, benzyloxyacetaldehyde, and tributylchlorostannane in the presence of zinc and aqueous ammonium chloride in tetrahydrofuran to give the corresponding δ-hydroxy-β-methylidenecarboxylic acid esters. In the absence of ammonium chloride, satisfactory yields of the products were obtained only in the reactions with prenal and benzyloxyacetaldehyde; these reactions involved lactonization of intermediate δ-hydroxy-β- methylidenecarboxylic acid esters, and the double carbon-carbon bond migrated to the conjugated position with the lactone carbonyl group. The condensation of β-ionylideneacetaldehyde with methyl 3-bromomethylbut-3-enoate was successfully used to obtain isotretinoin. Initial methyl 3-bromomethylbut-3- enoate was synthesized in a good yield from readily accessible ethyl 3,3-diethoxypropionate via cyclopropanation with ethylmagnesium bromide in the presence of titanium tetra(isopropoxide), oxidation of the acetal moiety to ester, and cleavage of the cyclopropane ring in intermediate methyl (1-methylsulfonyloxycyclopropyl)acetate.
An efficient commercial process for the preparation of isotretinoin
Salman, Mohammad,Babu, Suresh J.,Kaul, Vijay K.,Ray, Purna C.,Kumar, Naresh
, p. 302 - 305 (2012/12/24)
We describe an efficient process for the preparation of isotretinoin (13-cis isomer of vitamin A acid) in a single step starting from β-ionylidene acetaldehyde (5). The process conditions are convenient to operate on a commercial scale and afford isotretinoin of excellent quality; levels of related isomeric impurities such as tretinoin (all trans retinoic acid) and 9,13-di-cis-retinoic acid are extremely low. Thus, condensation of dienolate of methyl 3,3-dimethylacrylate with β-ionylidene acetaldehyde (5) followed by aqueous acidic workup afforded isotretinoin in >95% purity. The condensation reaction proceeds via in situ formation of lactone (8); furthermore, the reaction conditions have been optimized to exploit in situ generated methoxide anion for lactone ring opening to afford the desired product. Distinct advantages of this process are that it does not require isolation of intermediate lactone and utilizes in situ generated methoxide for lactone ring opening, thus obviating the need for an additional step and base. We also describe an optimized process for the preparation of β-ionylidene acetaldehyde (5), a key intermediate for isotretinoin.
A General Synthesis of 5,6-Dihydro-α-pyrones
Dugger, R.W.,Heathcock, Clayton H.
, p. 1181 - 1185 (2007/10/02)
Crotonate esters substituted at C-3 by alkyl, alkoxy, or dialkylamino groups are deprotonated and the resulting dienolates added to aldehydes and ketones.Kinetic reaction is at C-2 of the ester, leading to the isolation of 2-alkyl-3-hydroxy esters such as 3 and 4 if the reaction mixture is quenched at -70 deg C.However, retroaldolization occurs readily.If the initial reaction mixtures are allowed to warm to 15 deg C before workup, the isolated products are 5,6-dihydro-α-pyrones (such as 5), accompanied in some cases by the (E)-4-substituted crotonate (such as 6).The method has been applied to the synthesis of a series of retinoid lactones (5f,18,21a-c) which are of interest as potential antineoplastic agents.
