Terpenoidlerin aldol kondenzasyonu reaksiyonları
Aldol condensation reactions of some terpenoids
Yazar: AYŞE DAUT
Danışman: DOÇ.DR. OLCAY ANAÇ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü
Derece: Yüksek Lisans, 1993
Konu: Kimya = Chemistry
Dizin: Aldol kondenzasyonu = Aldol condensation ; Metil etil keton = Methyl ethyl ketone ; Metil heptenon = Methyl heptenone ; Salisilaldehit = Salicylaldehyde ; Terpenoidler = Terpenoids

Özet:
ÖZET Doğal bileşikleri sentetik yollardan elde edebilmek zamanımız Organik Kimyacıların başlıca amaçlarından birisidir. Farmasötik, kozmetik, pestisit gibi çok çeşitli endüstri kollarında kullanım alanı bulabilen doğal bileşikleri ve bunların türevlerini sentez etmek için çalışmalar süregelmektedir. Bu çalışmada terpen kökenli bazı aldehit/ketonların aldol konden- zasyonu reaksiyonları incelenmiştir. Bilindiği gibi Aldol Kondenzas- yonu Reaksiyonlarının keşfi çok eskilere dayanmaktadır. Buna karşılık reaksiyonlardan elde edilmek istenen ürün yönünden başarılı sonuç alın ması zaman zaman güçleşmektedir. Reaksiyonlardaki sorunlardan bazıları self-kondenzasyonlar, asimetrik ketonlarda birden fazla a-hidrojeni varlığındaki farklı aldol kondenzasyonu ürünleri oluşumu, oluşan ürünün polimerizasyona uğraması, Cannizaro, Claisen, Knoevenagel, Michael Katılması gibi reaksiyonlardır. Aldol kondenzasyonu reaksiyonlarında istenmeyen karışık (mixed) aldol ürünlerine engel olabilmek için en pratik yol çıkış bileşiklerin den birisinin ou-hidrojeni içermeyen bir aldehit, diğerinin de yine bir aldehit veya bir metilketon olarak seçilmesidir. Bundan sonra dikkat edilmesi gereken hususlar self-kondenzasyon verme tehlikesi olan reak- tanın diğer reaktanm fazlasına çok yavaş ilavesidir. Son olarak da oluşan ürünün reaksiyon ortamında polimerizasyona uğramasına engel ' olmak gerekir. Hem ürünün polimerizasyonuna engel olmak hemde reaksi yona uygun koşul bulabilmek için optimum pH'ın tesbiti önemlidir. Bu çalışmada os-hidrojeni içermeyen aldehit olarak sitral, salisil aldehit ve vanilin, reaksiyon ortağı bileşik olarak aseton, a- ve P- ionon, metiletilketon, metilheptenon kullanılmıştır. Gerçekleştiri len reaksiyonların yürüyüşü Gaz Kromatografisi, înce Tabaka Kromatog- rafisi ile izlenmiş ve ürünlerin saflaştırılmasında zaman zaman Prepa- ratif-TLC ve Kolon Kromatograf isinden yararlanılmıştır. Saflaştırılan ürünlerin tanımlanması İR ve 1H-NMR Spektrumları ile yapılmıştır. Çalışmada elde edilen aldol kondenzasyonu ürünlerinden bazıları orjinaldir. vı

Abstract:
ALDOL CONDENSATION REACTIONS OF SOME TERPENOIDS SUMMARY The so-called "aldol" product having p- hydroxy aldehyde function is obtained in an "aldol reaction". O OH 0 || HaOH/H20 | | 2CH3~ C-H ? CH3-CH-CH2-C-H Acetaldehyde 3-Hydroxyiutaiial (Aldol) The reaction also has many industrial applications such as producing starting materials for polymerization reactions, synthesis of perfume fragrances and also for the formation of five and six- membered rings. On the otherhand enzyme-catalyzed aldol reactions play important role in many biological processes. The normally expected product of an aldol condensation is an a, Ş- unsaturated aldehyde or ketone. The one major exception to this generalization is the situation in which p- hydroxy compound cannot undergo this dehydration reaction, when there is no hydrogen on the cm-carbon of the Ş- hydroxy compound. A generalized equation for the aldol condensation (and subsequent dehydration) is presented in Figure 1. Figure 1. The Aldol Condensation: a Generalized Equation The term aldol condensation has sometimes been applied to many so-called "aldol- type" condensations involving reaction of an aldehyde or ketone with a substance R2CHX or RCH(X)Y(X or Y: an activating group such as C02R, CONHR, CN,N02,S02CH3; R:alkyl, aryl or hydrogen). Mechanistically, of course these reactions are like aldol condensations. They produce and include Claisen, Knoevenagel, Reformatsky reactions. VllThe aldol condensation is catalyzed by acids, bases and amines. The base catalyzed mechanism, which was received much study, may be pictured by the following steps. The accepted mechanism for the reaction involves addition of the enolate anion from one molecule to the carbonyl group of the other CH, JU. OH0 fljO O iCH2-C-H :6:e CH2=C-H * H20 CH,-C-H + O e » ! CH2-C-H\ :6:9 CH2=C-H :OV CH, -CH-CH,-C-H :d:e O CH.-C H-CH,-C-H + H-OH- OH O OL-hH-aL-6-H + OH9 OH O O \\ H,Os OX OH/H20^ fj CH3-CH-CH2-C-H - £ '-*-> CH3-CH=CH-C-H + H20 2-Butenal ( Cxotonaldehyde) An a, p -unsaturated aldehyde Mixed aldol condensation reactions may take place when two different carbonyl compounds are allowed to react with each other. However, rather complex product mixtures may result if each compound reacts with itself as well as with the other component. Optimization of mixed aldol condensations; 1. One of the two carbonyl compounds must be more susceptible to nucleophilic attack. Usually this compound is an aldehyde with an unhindered carbonyl group. 2. The second compound must prefentially undergo enolate formation (or enol formation if acidic conditions are used). In many instances this preference is achieved because the first carbonyl compound has no «»-hydrogens (for example, if it is an aromatic aldehyde). vnx3. When the enolate is generated from an unsymmetrical ketone, reaction under typical basic conditions usually proceeds by enolate formation at the less substituted o-carbon of the ketone (This orientation can sometimes be reversed if acidic conditions are employed). There is also; - self -condensation of aldehydes, - mixed condensation of aldehydes, - self -condensation of ketones, - mixed condensation of ketones, - condensation of aldehydes with acyclic ketones, - condensation of aldehydes with alicyclic ketones, - condensation of aldehydes with alkyl aryl ketones. An important side reaction is self -condensation of aliphatic aldehydes (or ketones) (particularly those having an a-methylene group). Slow addition of these carbonyl compound may circumvent this difficulty. The best yields in aldol condensations are obtained when all reactants and solvents are carefully purified immediately before use. In this study aldol condensation reactions of some terpenoids with proper reactants were investigated in basic conditions having NaOH or aromatic amines. The reactions were observed by GC and TLC and the products were purified by column and preparative- TLC. The pure compounds obtained were controlled by GC and TLC and were identified by their IB. and in some cases ^-H-NMR spectra. The results were summarized in Table 1., Table 2. and Table 3. As can be seen in Table 1., the compounds I and II which were derived from salicyl aldehyde and a- and 0- ionone and VI which was obtained from citral and |3- ionone were new compounds. On the other- hand, as there was only a patent procedure in literature, a detailed procedure for the synthesis and identification of known compound III from salicyl aldehyde and methylheptenone were given. As the whole products obtained have polyfunctional groups and odoriferous properties, they might be used -as starting materials in flavour, fragrance, cosmetic, pharmaceutic and even in polymer industries. 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