Yeni Furil Halkası İçeren Kalkonların Ve Triazolinlerin Sentezi

Abstract

Bu çalışmada perklorik asit varlığında t-butilalkol ve asetik asitden elde dilen 2,4,6-trimetil perklorattan hidrojen peroksit mevcudiyetinde halka küçülmesi sonucu 2-asetil-3,5-dimetil foran elde edildi. Bu foran türevi 5 farklı (tiofen aldehit, pirol aldehit, p-flor benzaldehit, p-klor benzaldehit ve p-brom benzaldehit) aromatik aldehit ile reaksiyona sokuldu ve aldol kondensazyonu sonucu furil halkası içeren 5 tane yeni a,J3-doymamış bileşik elde edildi. Bu kalkonların yapılan spektral yöntemlerden yararlanılarak açıklandı ve ticari olarak satılan Tirimetil silil azid (TMS A) ile 3+2 siklodipolar katılma reaksiyonu sonucu 5 yeni A -1,2,3-triazolinler elde edildi. Pirilium tuzları ve kalkonlar gibi triazolinler de sentetik organik kimyada birçok bileşiklerin sentezi için önemli anahtar bileşiklerdir. Örneğin termal parçalanmaları sonucu oluşabilecek enaminlerin (nötral dönor syntonlar) alkilhalojenürler ile reaksiyonları sonucu 1,2 dionlar elde edilebilmektedir. Çalışmamız bu doğrultuda devam etmektedir.

Starting from hydrogen peroxide and 24,6-trialkylpyrilium salts 1, which are easily available by reaction of anhydrous t-butyl alcohol and acetic anhydride in the presence of perchloric acid 2-acyl-3,5-dialkyl furans 2 can be obtained in good yields by ring contraction. The present work reports the synthesis and spectral elucidation of the condensation products from such 2-acetyl-3,5-dialkylfurans and aromatic aldehydes In all cases the 5-and 3-alkyl groups are methyl. Under reaction condition similar to those used for obtaining chalcone from benzaldehyde and acetophenone, 2-acyl-3,5 dialkylfurans undergo condensation with aromatic aldehydes: thiophene aldehyde, pyrrol aldehyde p-fluoro benzaldehyde, p-chloro benzaldehyde, p-bromo benzaldehyde affording title compounds 3a-e. These new compounds are interesting starting materials for the synthesis of other heterocyclic compounds by Claisen condensation, Michael reaction, Robinson annulation and by 3+2 cyclo dipolar reactions. These a,P-unsaturated ketones are crystalline and may purified by recrystallization from ethanol (Table 1). Vibrational and H-NMR spectra (Fig 1,2^,4,5) confirm the structure of these componds. The a,|3-unsaturated carbonyl vibration appears at 1640-1650 cm". In our study 2,4,6 - trimetyl pyrillium perchlorate is used for the starting material for the synthesis of chalcones. Synthesis of 2,4,6-trimethyl pyrilium perchlorate is shown below: (CH3)3COH + 2 (CH3CO)20 + HCI04 -HpO -2CH3C02H This pyrylium salt is converted into 2-acetyl-3,5 dimethyl furan ring by contraction reaction with hydrojen peroxide and water vapor distillation. + H202 From acetyl furan two new chalcones are formed. l-(3,5-dimethyl-2-furoil)-2-(2- tiophenyl)-ethylene (3a) is formed by the reaction of acetyl furan and thiophenylaldehyde and the other l-(3,5- dimethyl-2- furoil)-2-(2-pyroil-)ethylene (3b) is formed by the reaction of acetyl furan and pyrolaldehyde CHf 0' ^ \ho 3 /OH 1 2 CHf "O'^CO CH=CH 3a XH3 ZH$ -CH3 NH \m Under reaction conditions similar to those used for obtaining chatcones from thiophene aldehyde and pyrolaldehyde, 2-acetyl-3,5-dialkyl furan 2 three new under goes condensations with p-fluoro benzaldehyde, p-chloro benzaldehyde and p-bromo benzaldehyde CHf 0 ^CO CH3 0HC-C6H4-X 1 0H- XH3- CHf ^ ^Sc -CH=CH C6H4-X X=CI,Br,F 3c-e v Table 1 Physical constants and I.R.data of compounds 3a-e H-NMR spectra were recorded in CDCI3. (Table 2) The large J coupling constants (15.63 Hz.) indicated that the vinylic protons are in E-configuration. The single peak at 6. 06-6.08 ppm in CDCI3 is due to the furanic proton in agreement with literature data. V / Hb H n,.. j - r 3a-e compounds Table 2 H-NMR chemical shifts of chalcones 3a-e in CDCI3 The 13C-NMR spectra(Figure 6) were recorded only for 3a in CDCI3. The assignments for chemical shifts (Table 3) were made using 2D-1H-13C-NMR corelation maps(Figure 4-7 and Figure 8)and a.p.t. spectra (Figure 9). Results are in good agreement with literature data. Table 3.C13-NMR chemical shifts (8TMS=0.00 ppm) of compound 3a in CDC13 HV4_3/CH3 5 CH3 u/vvr H.H CO- 6 CH= 7 The mass spectra were recorded only for compound 3 a (Figure 10) In the electron impact mass spectra the parent peak has medium intesity (53.35%). The base peak appears at m/z=l 11; The latter radical ion is the 3,5-dimethylfuroyl and appears at m/z=123 with an intensity of 64.07% The present work reports also the preparation of A2- 1,2,3 -triazolines starting from these new chalchones by 3+2 cyclodipolar reactions. In these reactions TMSA (trimethylsilylazide) is used as dipol. The purpose is to prepare triazolines and to examine that whether enamines are produced or not by thermal pyrolisis of triazolines. H R 1 V d c CO-CH=CH- H3 + (CH3)3Sh e -*N- Î e (CH3)3Si N N= © :N: \ & JR R^T» CO-CH-CH \/ ^Si(CH3)3 / d c CO-CH-CH Vs1.-N2 d c 'CT ^CO-C=CH H2N Like as pyrilium salts and chalcones enamines represent, more than any other heterocyclic system, a nodal point for many synthetic routes, they can function as neutral donors and have been attractive derivatives for monoalkylations with alkyl bromides or iodides and mono acylations with. Enamines of monoketones have been attractive derivatives for monoalkylations and monoacylations. In this enamine, the carbon atom which is the electophylic center can give 1, 2-diones with alkyl bromides or iodides. 2mol RX H3 i- 1 mol RX ii.H20 ©NR2 All reactions with trimetyl silylazide were carried out under purified nitrogen in an efficient hood. The furyl analogues of chalcones 3a-e were refluxed with the equimolar amount of trimethylsilylazide in xylene for 16hr. The solvent was removed by- evaporation at reduced pressure, and the residue was boiled with 50 ml of EtOHcooling and filtration afforded 4-(3,5-dimethyl-2-furoyl)-5-aryl-A -1,2,3- triazolines 4a-e. These triazolines are crystalline and the unreacted ketone was separated from the product by preparative TLC chromatography using CHCl3+PrOH(10: l)for 4a.b and CHCI3+C2H5OC2H5(10:5) for 4c,d,e. Yields varied from 40 to 81% (Table 4) Table 4 Physical constants and spectral data of compounds 4a-e The IR spectra recorded in KBr pellets showed for compound 4a a strong sharp band at 3300 cm" due to N-H stretching. The carbonlye frequency appeared at about 1720 cm". The H-NMR spectra were recorded only for compound 4a. The two protons connected with the two sp3 C atoms of the triazoline ring (He and Hd respectively) appear as doublets having coupling constant J of 10 Hz at 8 4.90 and 4.60 ppm; the NH group appeal as singlet at 6.95 ppm. A mixture of 0.9 g triazoline 4a and 25 ml of Pl^O evolved azot when stirred for 30 min. at 200°C. After removal of solvent at reduced pressure and addition of 50 ml. Et20, filtration affoded 0.3 g of unreacted triazoline 4a. The filtrate was chromatographed to give 0.5 g of 5a, m.p. 110-111 C. The Infrared spectra recorded m KBr pellets showed a broad at 3535-3440 cm" due to NH2 stretching. The carbonyl frequency appeared at about 1650 cm".