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Symmetrical and Asymmetrical Cyclopropenones: Synthesis and Study of Their Chemical Reactivity

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Symmetrical and Asymmetrical Cyclopropenones: Synthesis and Study of Their Chemical Reactivity The Open Organic Chemistry Journal, 2008, 2, 35-40 35 Open Access Symmetrical and Asymmetrical Cyclopropenones: Synthesis and Study of Their Chemical Reactivity Klimova Elenaa, Klimova Tatianaa, Lijanova Irinab, Domínguez Chávez Jorgeb, Hernández Ortega Simonb, Méndez Iturbide Danielc and Martínez García Marcos*,b aUniversidad Nacional Autónoma de México, Facultad de Química, Cd. Universitaria, Coyoacán, C.P. 04510, México D.F., México bUniversidad Nacional Autónoma de México. Instituto de Química, Cd. Universitaria, Coyoacán, C.P. 04510, México D.F., México cUniversidad Autónoma de Tlaxcala, Facultad de Ciencias de la Salud, San Pablo del Monte, C.P. 90920, Tlaxcala, México Abstract: Symmetrical and asymmetrical cyclopropenones with diferrocenyl, diaryl and aryl-ferrocenyl substituents were obtained and their chemical behavior was studied. 1-Ethoxy-2,3-diarylcyclopropenylium terafluoroborate selectively re- acts with MeLi, n-BuLi with formation of the 3,3-dialkyl-1,2-diarylcyclopropenes. The structures of 2,3-bis(4- methoxyphenyl) cyclopropenone (10), 2-ferrocenyl-3-(4-methoxyphenyl) cyclopropenone (11), 2-ferrocenyl-3- (naphthalen-1-yl) cyclopropenone (14) and 3,3-dimethyl-1,2-dianysol cyclopropene 19a were confirmed by X-ray crystal- lographic analysis. Keywords: Cyclopropenone, ferrocene, cyclopropenium cation, cyclopropene. The first cyclopropenilium cation, namely triphenylcy- Diarylcyclopropenone 2 was found to be able to react clopropenium, was synthesized and described by Breslow with several chemical reagents such as amines, hydrazines, and coworkers in 1957 [1], and shortly after that the corre- alcohols, thiols, organometallics and diazo-compounds [8]. sponding diphenylcyclopropenone was obtained [2]. Nowa- The synthesis of diferrocenylcyclopropenone 3 has been days, numerous investigations have been carried out with performed in our group [9]. It was found that the reactions of this class of cations [3], and in the last years they were pre- 3 with ethyl- and benzylmagnesium chlorides afforded not pared by various routes [3-8]. only 3,3-diethyl- and 3,3-dibenzyl-1,2-diferrocenylcyclo- Cl O propenes 4a and 4b, respectively (Equation 2), but also o products of nucleophilic opening of the three-membered ring 1.- 0 C 2HCl 2C H + AlCl4 + 5a,b and 6a,b. This result was attributed to the presence of 6 6 2.- H O 2 two ferrocenyl groups in the structure of the compound 3 Cl Cl 1 2 making its chemical behavior different from the reported previously for the diaryl cyclopropenones. Equation 1. Fc The diarylcyclopropenone 2 was obtained after hydroly- O Fc Fc R R R CH2 sis of the products of alkylation obtained by the reaction of RMgCl R C Fc C + C C + benzene or benzene derivatives with trichloro cyclopro- O Fc penium tetrachloroaluminate (1) (Equation 1) [6]. Further Fc Fc Fc Fc O H O 5a, study of this reaction showed that it takes place stepwise; at 3 4a, 6a, + b b b low temperature, a single chlorine atom in the C3C13 ion is replaced, whereas at room temperature, a mixture of mono- R= -CH2Ph (a); -CH2-CH3 (b) and disubstituted products is obtained [6]. Trisubstitution is not normally observed. From the point of view of the Fc= mechanism, the reaction shown in equation 1 is a Friedel- Fe Crafts alkylation, involving electrophilic substitution on the carbon of the benzene ring, and generally leads to the forma- tion of symmetrical diarylcyclopropenones. The common Equation 2. reagents for this reaction are aromatic hydrocarbons bearing In contrast to symmetrical diaryl- or diferrocenyl cyclo- weakly activating groups (alkyl) or weakly deactivating sub- propenones, their asymmetrical analogs with the aryl and stituents (halogen). ferrocenyl sustituents in the same molecule have not been *Address correspondence to this author at the Universidad Nacional synthesized and studied up to now. At the same time, the Autónoma de México. Instituto de Química, Cd. Universitaria, Coyoacán, influence of the ferrocenyl fragment on regio- and stereo- C.P. 04510, México D.F., México; E-mail: [email protected] 1874-0952/08 2008 Bentham Open 36 The Open Organic Chemistry Journal, 2008, Volume 2 Elena et al. O O Cl Cl 1 1 1.- AlCl3, CH2Cl2 + + 2´ + 3 + Fe 2.- H O 1´ 2 3´ 3 2 3 2 4 Cl Cl OCH3 Fe CH3O 4´ OCH3 9 H3CO 11 7 8 10 4 O O Cl Cl 1 1 1.- AlCl , CH Cl 3 3 2 2 3´ 2´ + + 3´ + + Fe 2´ 2.- H O 1´ 2 2 3 1´ 4´ 3 2 4´ Cl Cl Fe 7 14 12 9 7´ 10´ 13 8´ 9´ O O 2´ 3´ Cl Cl 1 2´ 3´ 1´ 4´ 1 1.- AlCl , CH Cl 3 2 2 + 3 + 1´ 4´ + + 2.- H O Fe 2 3 2 10´ 9´ 2 3 10´ Cl Cl 9´ 8´ 5´ Fe 16 17 8´ 5´ 9 7´ 7 15 6´ 7´ 6´ Scheme 1. Synthesis of symmetrical and asymmetrical cyclopropenones. chemistry of aryl-ferrocenyl cyclopropenones and its chemi- tained by crystallization from hexane. Fig. (1 and 2) show cal properties deserve to be studied. the crystal structures of the compounds 10 and 11. In the present work, we report the synthesis of symmetri- 01 cal diaryl and asymmetrical aryl-ferrocenyl cyclopropenones and the behavior of the 1-ethoxy-2,3-diarylcyclopropenium C1 C5 cation in the reactions with organolithium reagents. C6 RESULTS AND DISCUSSION C2 C10 The cyclopropenones 3, 10, 11, 13, 14, 16 and 17 were C3 C7 C4 obtained from tetrachlorocyclopropene 7 and the mixtures of C16 C2 ferrocene-anisole, ferrocene-naphthalene and ferrocene- C11 C8 anthracene in anhydrous CH2Cl2 using catalytic amounts of C3 aluminum chloride. C12 C15 The following signals were observed in the 1H NMR spectrum of compound 10: one singlet at 3.91 for the C13 methoxy groups and two doublets at 7.06 and 7.93 for the C14 1 aryl groups. In the H NMR spectrum of the asymmetrical C17 cyclopropenone (11) were observed the signals of the 03 methoxy group (one singlet at 3.90), the ferrocenyl group (three characteristic signals at 4.22, 4.59 and 4.89) and the Fig. (1). Crystal structure of the symmetrical compound (10). Se- aryl group (two doublets at 7.06 and 8.84). lected bond lengths [Å]: C(1)-C(2)= 1.412, C(1)-C(3)= 1.408, C(2)- Crystals of 2,3-bis(4-methoxyphenyl) cyclopropenone C(3)= 1.356, C(1)-O(1)= 1.223. Selected bond angles (º): C (3)- (10) and 2-ferrocenyl-3-(4-methoxyphenyl) cyclopropenone C(1)-C(2)= 57.48, C(3)-C(2)-C(1)= 61.11, C(2)-C(3)-C(1)= 61.41. (11) suitable for X-ray crystallographic studies were ob- Symmetrical and Asymmetrical Cyclopropenones The Open Organic Chemistry Journal, 2008, Volume 2 37 The following signals were observed in the 1H NMR In the 1H NMR spectrum of compound 16 the following spectrum of the compound 13: one doublet assigned to the signals assigned to the anthracenyl group were observed: one naphthyl group at 8.94 with a coupling constant J = 8.5 Hz singlet at 8.86 due to the two protons in the positions 10`; due to the proton in the position 7´, three doublets at 8.38, one doublet at 8.41 with a coupling constant J = 6.9 Hz for 8.18 and 7.90, all with coupling constants J = 7.0 Hz for the the protons in the positions 1` and 8´; double of doublets at protons in the positions 2´, 4´ and 10´, respectively, and two 8.1 with coupling constants J = 6.4 Hz ascribed to the pro- multiplets at 7.85 and 7.65 due to the protons in the posi- tons in the positions 4´ and 5´; one multiplet at 7.4 due to tions 3´, 8´, and 10´. In the 13C NMR spectrum of this com- the protons in the positions 3´,6´and 2´,7´. In the 13C NMR pound, the most important signals observed were at 146 spectrum of compound 16 were observed the signals charac- corresponding to the sp2 carbon of the cyclopropene and at teristic for the anthracene moiety at 111.3-134.8, the signal 155.5 which is the signal characteristic for the carbonyl due to the sp2 carbons C=C of the cyclopropene ring at group. 148.1, and the most important signals of the quarternary carbons of the cyclopropene at 156.7 and the signal charac- C20 teristic for the carbonyl group at 155.5. For the asymmetri- C16 C19 cal cyclopropenone 17, in the 1H NMR spectrum were ob- served the signals of the ferrocenyl (three characteristic sig- 01 C17 C18 nals at 4.24, 4.66 and 5.01) and the anthracenyl group (two C1 Fe1 doublets at 7.06 and 7.84 with coupling constants J = 7.1 C5 C15 C6 Hz and J = 1.3 Hz, respectively); also two sets of multiplets C4 C11 C14 C2 were observed at 7.9-8.1 and at 8.32 due to the protons in C10 C3 the positions 1´, 4´, 5´and 8´. C9 C13 C7 C12 XRD studies of compounds 10, 11 and 14 showed that C8 02 the presence of two large and heavy substituents in their molecules leads to the distortion of the cyclopropenone Fig. (2). Crystal structure of the asymmetrical compound (11). structure and to enlargement of the internal angles in the Selected bond lengths [Å]: C(1)-C(2)= 1.412, C(1)-C(3)= 1.399, positions 2 and 3. C(2)-C(3)= 1.362, C(1)-O(3)= 1.223. Selected bond angles (º): C (3)-C(1)-C(2)= 57.8, C(3)-C(2)-C(1)= 60.7, C(2)-C(3)-C(1)= 61.5.
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