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Journal article

A novel aldol condensation alternative: a,b-unsaturated aldehydes from 3-hydroxy-1-alkynes via dihydrodioxepins

The controlled aldol condensation between an aliph. ketone and an acetaldehyde equiv. remains a challenge. One soln. to this evergreen problem consists of the nucleophilic addn. of acetylene to the ketone and the subsequent isomerization of the resulting 3-hydroxy-1-alkyne to the corresponding 2-alkenal. So far, however, the latter step could only be executed with acid-insensitive substrates. The authors now present a milder, three-step method which extends the scope of the procedure considerably. In the first step, the 3-hydroxy-1-alkynes RCMeOHC.tplbond.CH (R = Me, Ph, Me2CH:CHCH2CH2, Q, CH2:CH, HC.tplbond.C) are converted into 2-propynyl ethylene glycol monoethers RCMe(OCH2CH2OH)C.tplbond.CH; these then undergo base-catalyzed cyclization to give the dihydro-1,4-dioxepins (I and II; R = same as above), which are hydrolyzed in acidic medium in the third and final step to give ketones RCMeOHCOMe (R = same as above) and a,b-unsatd. aldehydes RCMe:CHCHO (R = same as above), resp. Thus, RCMe(OCH2CH2OH)C.tplbond.CH (R = Q) (prepn. given) was treated with Me3COK in Me3COH for 12 h at 85 Deg to give a 4:96 mixt. of I (R = Q) and II (R = Q) in 95% yield. II (R = Q) was hydrolyzed by 6 M HCl in THF under reflux for 5 h to give 90% RCMe:CHCHO (R = Q). [on SciFinder (R)]

    Keywords: Hydrolysis (novel aldol condensation alternative in prepn. of a ; b-unsatd. aldehydes from 3-hydroxy-1-alkynes by base-catalyzed cyclization of 3-(hydroxyethoxy)-1-alkynes to dihydrodioxepins and hydrolysis); Aldehydes Role: SPN (Synthetic preparation) ; P ; aldol condensation alternative; unsatd aldehyde prepn; hydroxyethoxyalkyne cyclization dihydrodioxepin; dihydrodioxepin hydrolysis

    Note:

    CAN 129:316398 30-20 Terpenes and Terpenoids Institut Chimie Organique,l'Universite Batiment Chimie,Lausanne,Switz. Journal 0947-6539 written in English. 108-86-1 (Bromobenzene); 127-66-2 (2-Phenyl-3-butyn-2-ol); 865-47-4; 3230-69-1 (3-Methylpent-1-en-4-yn-3-ol); 3741-38-6 (Ethylene sulfite); 14398-40-4; 17974-59-3 (Ethynyl-b-ionol); 25597-36-8; 29171-20-8; 76783-21-6 (3-Methylpent-1,4-dyn-3-ol); 88692-62-0; 214967-54-1; 214967-57-4; 214967-58-5; 214967-59-6 Role: RCT (Reactant), RACT (Reactant or reagent) (novel aldol condensation alternative in prepn. of a,b-unsatd. aldehydes from 3-hydroxy-1-alkynes by base-catalyzed cyclization of 3-(hydroxyethoxy)-1-alkynes to dihydrodioxepins and hydrolysis); 89897-07-4P; 214967-60-9P; 214967-61-0P; 214967-62-1P; 214967-63-2P; 214967-64-3P; 214967-65-4P; 214967-66-5P; 214967-67-6P; 214967-68-7P; 214967-69-8P; 214967-70-1P; 214967-75-6P; 214967-76-7P; 214967-78-9P; 214967-80-3P ((Z)-2-(Benzylidene)-3,3-dimethyl-1,4-dioxane) Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (novel aldol condensation alternative in prepn. of a,b-unsatd. aldehydes from 3-hydroxy-1-alkynes by base-catalyzed cyclization of 3-(hydroxyethoxy)-1-alkynes to dihydrodioxepins and hydrolysis); 106-26-3P; 107-86-8P (3-Methyl-2-butenal); 141-27-5P; 3917-41-7P; 20432-42-2P; 21866-70-6P ((E)-3-Phenyl-2-butenal); 21878-52-4P ((Z)-3-Phenyl-2-butenal); 25428-61-9P; 25428-62-0P; 52421-93-9P; 54226-17-4P; 54716-03-9P; 74336-72-4P; 94034-66-9P Role: SPN (Synthetic preparation), PREP (Preparation) (novel aldol condensation alternative in prepn. of a,b-unsatd. aldehydes from 3-hydroxy-1-alkynes by base-catalyzed cyclization of 3-(hydroxyethoxy)-1-alkynes to dihydrodioxepins and hydrolysis)

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    Record created on 2006-03-03, modified on 2016-08-08

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