Piperidine Acetate Research Articles

Concise preparation of the (3E,5Z)-alkadienyl system. New approach to the synthesis of principal insect sex pheromone constituents.

A new rapid and low-cost preparation of the (3E,5Z)-3,5-alkadienyl system, encountered in several insect pheromone constituents, was developed. Knoevenagel condensation of (E)-2-alkenals with ethyl hydrogen malonate in dimethyl sulfoxide, in the presence of a catalytic amount of piperidinium acetate, led to a mixture of geometrical isomers of ethyl 3,5-alkadienoates and ethyl 2,4-alkadienoates, from which the (3E,5Z)-3,5-alkadienoate was conveniently separated, by the use of urea inclusion complex formation. The importance of this procedure has been illustrated by the preparation of the (3E,5Z)-3,5-tetradecadienoic acid (megatomoic acid) 1, the (3E,5Z)-3,5-dodecadienyl acetate 2, and the (3E,5Z)-3,5-tetradecadienyl acetate 3. These compounds are the main components of insect sex pheromones and constitute synthetic targets of considerable interest for the semiochemical community.

Synthesis of novel 6-enaminopurines.

Two different approaches have been used for the synthesis of 6-enaminopurines 6 from 5-amino-4-cyanoformimidoyl imidazoles. In the first approach imidazoles 1 were reacted with ethoxymethylenemalononitrile or ethoxymethylenecyanoacetate under mild experimental conditions and this led to 9-substituted-6-(1-amino-2,2-dicyanovinyl) purines 6a-f or 9-substituted-6-(1-amino-2-cyano-2-methoxycarbonylvinyl) purines 6g-k. These reactions are postulated to occur through an imidazo-pyrrolidine intermediate 7, which rapidly rearranges to the 6-enaminopurine 6. In the second approach 6-methoxyformimidoyl purines 3, prepared in two efficient steps from 5-amino-4-cyanoformimidoyl imidazoles 1, were reacted with malononitrile and methylcyanoacetate with a mild acid catalysis (ammonium acetate or piperidinium acetate) to give 6-enaminopurines 6a, 6d, 6f, 6g and 6k in very good yields. Only low yields were obtained for the 6-enaminopurine 6j, as competing nucleophilic attack on C-8 of either 3d or 6jcauses ring opening with formation of pyrimido-pyrimidines 11 and 10a respectively.

Ring transformations of heterocyclic compounds. XXII. Pyrido[1,2‐a]indolium salts from 2‐methyl‐3H‐indoles by pyrylium mediated three carbon annelation

AbstractThe synthesis of pyrido[1,2‐a]indolium perchlorates 8,11 from 2,4,6‐triarylpyrylium perchlorates 1 and 2‐methyl‐3H‐indoles 6,9 in the presence of a basic condensing agent (anhydrous sodium acetate, piperidine acetate, triethylamine/acetic acid, triethylamine) in ethanol by a 2,4‐[C3+C2N] pyrylium ring transformation is reported. Spectroscopic data of the transformation products and their mode of formation are discussed.

A simple 1,5 → 1,3-diketone rearrangement

Abstract 1-Aryl-1,3-diketones 4-7 were prepared by reaction of the corresponding 1-aryl-1,5-diketones 2b with piperidinium acetate in refluxing C6H6.

Improvement on the synthesis of (E )-alk-3-enoic acids

(E)-Alk-3-enoic acids have been prepared in high yield (85–90%) and excellent stereoselectivity (98–99%) by a modified Knoevenagel condensation of a straight carbon chain aldehyde with malonic acid, in dimethyl sulfoxide (DMSO) or dimethylformamide (DMF) at 100 °C, in the presence of piperidinium acetate as catalyst. Condensation of the aldehyde with a monoester of malonic acid, under the above conditions, gave the corresponding ester of (E)-alk-3-enoic acid in high yield (76–82%) and good stereoselectivity (90–92%). Condensation of the aldehyde with cyanoacetic acid gave the β,γ-unsaturated nitrile in moderate yield (35–40%) without stereoselectivity.

C-Alkylation of Methyl leuco-6-Deoxykermesate by Aldol Reactions and its Application to Synthesis of Carminic Acid

In a non-aqueous medium in the presence of piperidinium acetate, methyl leuco-6-deoxykermesate reacts in aldol fashion with aldehydes regioselectively to give 6-alkyl products while under aqueous alkaline conditions over a prolonged time, 7-alkyl compounds are selectively formed; the structures of the 6-alkyl series was confirmed by an X-ray crystal structure determination of the 6-methyl member, namely methyl 3,5,8-trihydroxy-1,6-dimethylanthra-9,10-quinone-2-carboxylate; in aqueous alkaline conditions during a short mild reaction period, intermediate 7-α-hydroxyalkyl compounds can be isolated, and in an application to a synthesis of 6-deoxycarminic acid, the aldol reaction of 2,3,4,5,6-penta-O-benzyl-D-glucose with methyl leuco-6-deoxykermesate was examined.

Thioalkylation of Meldrum's Acid with Dialdehydes. Isopropylidene cis-2-Hydroxy-6-phenylthiocyclohexane-1,1-dicarboxylate Derivatives

Reaction of Meldrum's acid, thiophenol and gluteraldehyde in aqueous acetonitrile with piperidine acetate affords a 70% yield of isopropylidene cis-2-hydroxy-6-phenylthiocyclohexane-1,1-dicarboxylate. The reaction is very general. It can be applied to dialdehydes derived in a many ways using many different thiols. © 1997 Elsevier Science Ltd.

A facile synthesis of 2,5-dimethyl-4-hydroxy-3(2H)-furanone [2- (or 5-) methyl 14C] (furaneol [2- (or 5-) methyl 14C

A convenient one-step synthesis of 14C-labelled 2,5-dimethyl-4-hydroxy-3(2H)-furanone (furaneol) was accomplished by a piperidine acetate catalyzed Maillard-type reaction of commercially available fucose L-[1-14C]. This important aroma compound found in strawberry fruits, obtained in ≥ 90 % radiochemical purity, should prove useful in in-vivo metabolism studies. © 1997 John Wiley & Sons, Ltd.

Reactions of 6,6-dimethyl-4,5-dioxo-i-phenyl-4,5,6,7-tetrahydroindazole with 1,3-cyclanediones

The condensation of 6, 6-dimethyl-4, 5-dioro-l -phenyl-4, 5, 6, 7-tetrahydroindazole with the 1, 3-cyclanediones 1,3-indanedione and barbituric acid in the presence of piperidine acetate gave 4-(1,3-indanedion-2-ylidene)-and 4-(2, 4, 6-trioxo-4, 5-dihydro-5 pyrimidylidene)-5-oxo-l -phenyl-4, 5, 6, 7-tetrahydroindazoles respectively. With hydrazine hydrate the former readily gave 4, 4-dimethyl-12-oxo-3-phenyl-4, 5-dihydro-10H-indeno(3, 2-c]pyrazolo(4, 5-flcinnoline.

Ringtransformationen heterocyclischer Verbindungen. VII. 2,4,5-Triaryl-benzophenone aus 2,4,6-Triaryl-pyryliumsalzen und Arylacetaldehyden: Erste Pyryliumringtransformationen mit Aldehyden als Kohlenstoffnucleophile

Ring Transformations of Heterocyclic Compounds. VII. 2,4,5-Triarylbenzophenones from 2,4,6-Triarylpyrylium Salts and Arylacetaldehydes: First Pyrylium Ring Transformations with Aldehydes as Carbon Nucleophiles 2,4,6-Triarylpyrylium salts 1 react with arylacetaldehydes 2 in the presence of sodium acetate in ethanol by a 2,5-[C4+C2] ring transformation to give 2,4,5-triarylbenzophenones 3 in high yield. Besides the sodium acetate, sodium methanolate, triethylamine, triethylamine/acetic acid or piperidine acetate can be applied as condensing agent. The reaction represents the first pyrylium ring transformation initiated by aldehydes.

Ringtransformationen heterocyclischer Verbindungen, VI. 3‐Nitrobenzonitrile aus 2,4,6‐Triarylpyryliumsalzen und Nitroacetonitril

Ring Transformations of Heterocyclic Compounds, VI. – 3‐Nitrobenzonitriles from 2,4,6‐Triarylpyrylium Salts and Nitroacetonitrile2,4,6‐Triarylpyrylium salts 1 react with nitroacetonitrile in the presence of sodium acetate, triethylamine, triethylamine/acetic acid or piperidine acetate to give 3‐nitrobenzonitriles 2. In the course of this 2 6‐[C5 + C] pyrylium ring transformation a nitro group is shifted to C‐3 of the benzene ring formed. Structural elucidation of the reaction products 2 is based on an X‐ray structure determination of the methoxyphenyl derivative 2c.

Synthesis of 3-Alkylcoumarins and 3-Alkyl-α,β-unsaturated δ-Lactones from 3-Diethylphosphonocoumarins, 3-Diethylphosphonolactones and Aldehydes

The treatment of salicylaldehyde 1 and derivatives 2-4 with triethyl phosphonoacetate 5 in refluxing toluene using piperidine acetate and β-alanine affords 3-diethyl phosphonocoumarins 6-9. By hydrogenation of the compounds 6-9, 3-diethylphosphono-3,4-dihydrocoumarins 10-13 have been obtained. The compounds 10-13 react with the aromatic aldehydes 14-18, under Wittig-Horner conditions, to give 3-alkyl-coumarins 19-24 in satisfactory yields. The reaction of 3-diethyl-phosphonolactones 25, 26 with isatin 27 and 5-bromoisatin 28, under similar reaction conditions, leads to 3-alkyl-α,β-unsaturated δ-lactones 29-31

Stereoselective Access to Tetrahydropyranylacetic Acid Derivatives. Simple Synthesis of (+)-(S,S)-(cis-6-Methyltetrahydropyran-2- yl)acetic Acid

The reaction of the lactols 1a-1d, with malonic acid in hot dimethyl sulfoxide, in the presence of piperidinium acetate as catalyst, gives the corresponding (tetrahydrofuran-2-yl)acetic acids 2a, c and (tetrahydropyran-2-yl)acetic acids 2b, d in high yield (65-75%). While the synthesis of the (6-methyltetrahydropyran-2-yl)acetic acid (2d) is highly stereoselective (cis/trans ratio 20:1), no stereoselection was observed with the (5-methyltetrahydrofuran-2-yl)acetic acid (2c) (cis/trans ratio 1:1). This reaction was applied for the synthesis of natural (+)-(S,S)-cis-6-methyltetrahydropyran-2-yl)acetic acid (7), minor constituent of the glandular secretion of the civet cat

Pyryliumverbindungen. 46. 4-Aroyl-fluoren-9-one durch Ringtransformation von 2,4,6-Triaryl-pyryliumsalzen mit Indan-1,3-dion

Pyrylium Compounds. 46. 4-Aroyl-fluoren-9-ones by Ring Transformation of 2,4,6-Triarylpyrylium Salts with Indan-1,3-dione The ring transformation of 2,4,6-triarylpyrylium salts 1 with indan-1,3-dione in the presence of a condensing agent such as piperidine acetate, triethylamine/acetic acid, triethylamine or sodium acetate leads to 4-aroyl-1,3-diaryl-fluoren-9-ones 6. As reaction medium aliphatic alcohols (methanol, ethanol), dipolar aprotic solvents (acetonitrile, dimethylformamide) or chlorinated hydrocarbons (methylene chloride, chloroform) can be used. The structure of the novel compounds 6 was confirmed by spectroscopic methods as well as by independent synthesis of the fluorenone 6a.

Pyryliumverbindungen. 42. Benzocycloalkenone und Dihydro‐2H,7H‐1‐benzopyranone aus 2,4,6‐Triaryl‐pyryliumsalzen und Cycloalkan‐1,2‐dionen

Pyrylium Compounds. 42. Benzocycloalkenones and Dihydro‐2H,7H‐1‐benzopyranones from 2,4,6‐Triarylpyrylium Salts and Cycloalkane‐1,2‐diones2,4,6‐Triarylpyrylium salts 1 react with cycloalkane‐1,2‐diones 2 in the presence of an appropriate condensing agent to yield benzocycloalkenones 3. Thus, sodium acetate and cyclo‐hexane‐1,2‐dione (2a) lead to the dihydro‐2H‐naphthalenones 3a–i, whereas with cycloheptane‐1,2‐dione (2b) and piperidine acetate, triethylamine or sodium acetate the tetrahydro‐5H‐benzo‐cyclohepten‐5‐ones 3j–r are formed. As shown for the example 3a, j → 4a, b, benzocycloalkenones of type 3 can be converted into phthalazines 4 on heating with hydrazine in ethanol. By reaction of the dione 2a and an equimolar mixture of triethylamine and acetic acid or morpholine acetate with the salts 1 5,6‐dihydro‐2H,7H‐1‐benzopyran‐8‐ones 5 are obtained as a result of a new type of ring transformation. The pyrans 5 can be cleaved with perchloric acid in ethanol to 5,6,7,8‐tetrahydro‐8‐oxo‐1‐benzopyrylium perchlorates 6. If the pyrans 5 are heated with sodium acetate in ethanol, a conversion to benzocycloalkenones 3 is achieved (cf. 5a → 3a). The structure of the new compounds was established by spectroscopic methods.

Pyryliumverbindungen. 44 [1]. 2‐(2‐Hydroxy‐3‐oxo‐cycloalk‐1‐enyl)‐2H‐thiopyrane aus 2,4,6‐Triaryl‐thiopyryliumsalzen und Cycloalkan‐1,2‐dionen

Pyrylium Compounds. 44. 2‐(2‐Hydroxy‐3‐oxo‐cycloalk‐1‐enyl)‐2H‐thiopyranes from 2,4,6‐Triarylthiopyrylium Salts and Cycloalkane‐1,2‐diones2,4,6‐Triarylthiopyrylium salts 5 react with cyclopentane‐1,2‐dione (2a) or cyclo‐hexane‐1,2‐dione (2b) in the presence of an appropriate acid binding agent (e.g. sodium acetate, piperidine acetate, triethylamine/acetic acid, triethylamine) to give the hitherto unknown 2‐(2‐hydroxy‐3‐oxo‐cycloalk‐1‐enyl)‐2H‐thiopyranes 6. – The structure of the novel compounds was established by n.m.r., i.r. and u.v. spectroscopic methods.

Pyryliumverbindungen. 43 [1]. Arylsubstituierte 5‐(2‐Dialkylamino‐thiazol‐5‐yl)‐pentadienone aus 2,4,6‐Triaryl‐pyryliumsalzen und 2‐Dialkylamino‐4‐arylthiazolen

Pyrylium Compounds. 43. Arylsubstituted 5‐(2‐Dialkylamino‐thiazol‐5‐yl)‐pentadienones from 2,4,6‐Triarylpyrylium Salts and 2‐Dialkylamino‐4‐aryl‐thiazoles2,4,6‐Triarylpyrylium salts 1 react with 2‐dialkylamino‐4‐aryl‐thiazoles 7 (used in substance or prepared in situ from α‐thiocyanato‐acetophenones 9) in the presence of an appropriate acid‐binding agent (e.g. piperidine acetate or sodium acetate) to give 5‐(2‐dialkylamino‐4‐aryl‐thiazol‐5‐yl)‐1,3,5‐triaryl‐penta‐2,4‐dien‐1‐ones 8. As reaction medium aliphatic alcohols (ethanol, n‐propanol), dipolar aprotic solvents (acetonitrile) or chlorinated hydrocarbons (methylene chloride, chloroform) can be used. On the other hand, under the same conditions 2‐amino‐4‐phenyl‐thiazole (10) reacts with salts of type 1 via pyrylium ring transformation yielding 2,4,6‐triaryl‐1‐(4‐phenyl‐thiazol‐2‐yl)‐pyridinium perchlorates 11.

Pyryliumverbindungen. 41. 7aH‐Cyclopenta[b]pyran‐7‐one durch Ringtransformation von 2,4,6‐Triaryl‐pyryliumsalzen mit acyclischen 1,2‐Diketonen

Pyrylium Compounds. 41. 7aH‐Cyclopenta[b]pyran‐7‐ones by Ring Transformation of 2,4,6‐Triarylpyrylium Salts with Acyclic 1,2‐DiketonesReaction of 2,4,6‐triarylpyrylium salts 1 with acyclic 1,2‐diketones 2 (CH3COCOR, R = Me, Ph) in the presence of an appropriate condensing agent (e.g. piperidine acetate, triethyl‐amine/acetic acid, sodium acetate) yields the hitherto unknown 2,4,5,7a‐substituted 7aH‐cyclopenta[b]pyran‐7‐ones 3 as a result of a new type of ring transformation (2,5‐[C4O+C]/2,3‐[C2+C3]). A characteristic feature of compounds 3 is their ability to undergo electrophilic substitutions. Thus, stepwise bromination of the 7a‐methyl derivative 3a in acetic acid affords 6‐bromo‐7a‐methyl‐2,4,5‐triphenyl‐cyclopenta[b]pyran‐7‐one (4) and 3,6‐dibromo‐7a‐methyl‐2,4,5‐triphenyl‐cyclopenta[b]pyran‐7‐one (5); analogously, nitration of 3a leads to 7a‐methyl‐6‐nitro‐2,4,5‐triphenyl‐cyclopenta[b]pyran‐7‐one (6), indicating that position 6 is the favoured position for electrophilic substitutions. Contrary to the 3,5‐unsubstituted pyrylium salts 1, the 3,5‐dimethyl‐2,4,6‐triphenyl‐pyrylium perchlorate (13) reacts with 1,2‐diketones 2 through a 2,6‐[C5+C] transformation to give arylsubstituted 1,2‐diones 14. The structure of the new compounds was determined by spectroscopic methods and by a single crystal X‐ray analysis of the dibromo derivative 5.

Thioalkylation of Meldrum's Acid: Protected alkylidene derivatives of isopropylidene malonate

AbstractThioalkylated Meldrum's acid is easily by treatment of Meldrum's acid with an aldehyde and thiophenol in the presence of catalytical amounts of piperidinium acetate (→1–6, Table 1). The adducts 1–6 are crystalline, stable compounds and they can be caused to react directly with nucleophiles and dienes (see 3→7–12, Scheme 1). The regeneration of the parent olefin is effected thereby by simply dissolving the adduct under neutral or basic conditions. Extension of this method to thiocarboxylic acids allowed the preparation of the corresponding formaldehyde derivatives 13 and 15 (Table 3).

ChemInform Abstract: Pyrylium Compounds. Part 36. Substituted Benzoic Acid Esters from 2,4,6‐Triarylpyrylium Salts and α‐Ketocarboxylic Acid Esters.

AbstractDepending on the amount of piperidine acetate, the reaction of the salts (I) with the esters (II) and/or (IV) yields the products (III) and (V) or (VI) and (VII).