Tetraphenylcyclopentadienone synthesis

C ( propyl) N phenylmtrone to N phenylmaleimide, 46, 96 semicarbazide hydrochloride to ami noacetone hydiochlonde, 46,1 tetraphenylcyclopentadienone to diphenyl acetylene, 46, 44 Alcohols, synthesis of equatorial, 47, 19 Aldehydes, aromatic, synthesis of, 47, 1 /3-chloro a,0 unsaturated, from ke tones and dimethylformamide-phosphorus oxy chloride, 46, 20 from alky 1 halides, 47, 97 from oxidation of alcohols with dimethyl sulfoxide, dicyclohexyl carbodumide, and pyndimum tnfluoroacetate, 47, 27 Alkylation, of 2 carbomethoxycyclo pentanone with benzyl chloride 45,7... 

The reaction has been shown to involve a stereospecific syn-addition with respect to the dienophile. For example, the reaction of 2,3-dimethylbuta-1,3-diene with maleic anhydride gives cis-l,2,3,6-tetrahydro-4,5-dimethylphthalic anhydride (Expt 7.20). An example of the use of a quinone as the dienophile is provided by the synthesis of cis-1,4,4a,9a-tetrahydro-2,3-dimethyl-9,l0-anthra-quinone which upon dehydrogenation (most simply by the action of oxygen upon its solution in alcoholic potassium hydroxide) yields 2,3-dimethylanthra-quinone (Expt 7.21). Tetraphenylcyclopentadienone (tetracyclone) readily undergoes the addition of dienophiles, such as maleic anhydride, to give an adduct, which then extrudes a molecule of carbon monoxide on heating, as in the preparation of 3,4,5,6-tetraphenyldihydrophthalic anhydride (Expt 7.22). 

As an extension of work on synthesis of strained cycloalkynes, trans- and tw-cyclopropane-fused medium ring (9-11-membered) cycloalkynes 108-111 and 113 were synthesized by thermolysis of 1,2,3-selenadiazoles 63, 105-107, and 112 with copper powder at 190-240 °C (Scheme 3) <1997LA1557>. /ra j-Bicyclo[7.1.0]dec-2-yne 108 is highly strained and has a low kinetic stability toward polymerization. Only traces of compound 108 were detected in the thermolysis of selenodiazole 63. The trapping with tetraphenylcyclopentadienone yielded an adduct 114 in 20% yield, whereas precursor 105 gave product 115 in 44% yield. 

Both the organometallic methods of phenyl-phenyl coupling (PPP synthesis) and the repetitive Diels-Alder reaction between tetraphenylcyclopentadienones and arylacetylenes toward branched polyphenylenes can be modified for the synthesis of structurally related oligomers (see also section 1.4.). Thus,... 

Cyclopentadienone is an elusive compound that has been sought for many years but with little success. Molecular orbital calculations predict that it should be highly reactive, and so it is it exists only as the dimer. The tetraphenyl derivative of this compound is to be synthesized in this experiment. This derivative is stable, and reacts readily with dienophiles. It is used not only for the synthesis of highly aromatic, highly arylated compounds, but also for examination of the mechanism of the Diels-Alder reaction itself. Tetraphenylcyclopentadienone has been carefully studied by means of molecular orbital methods in attempts to understand its unusual reactivity, color, and dipole moment. In Chapter 48 this highly reactive molecule is used to trap the fleeting benzyne to form tetraphenylnaphthalene. Indeed, this reaction constitutes evidence that benzyne does exist. 

In the attempted synthesis of twisted polycycle 1,2,3,4-tetraphenylfluorenoM, 9-g/i]quinoline, R.A. Pascal Jr. et al. used the Combes quinoline synthesis to assemble the azaaceanthrene core. Oxidation with DDQ was followed by a Diels-Alder reaction with tetracyclone (tetraphenylcyclopentadienone) to afford the corresponding cycloadduct. However, the last decarbonylation step of the sequence failed to work even under forcing conditions, presumably due to steric hindrance. 

This reaction provides quantities of benzoin for use in the multistep synthesis of hexaphenylbenzene (see Experiment [A4ab])- Benzoin is synthesized in this first step of the a series of the Sequential Experiments. In this sequence of reactions, benzoin is converted by oxidation (Experiment [A2a]) to benzil and then to tetraphenylcyclopentadienone (Experiment [A3a]).The latter compound undergoes a Diels-Alder addition with diphenylacetylene (Experiment [A3b]) to give hexaphenylbenzene (Experiment [A4ab]). 

Purpose. Benzil is the second of three synthetic intermediates in the a series of Sequential Reactions, which lead to the synthesis of hexaphenylbenzene. Benzoin, the starting material for this step, is prepared in Experiment [AIJ. Benzil, the product formed in the present reaction, is used in the synthesis of tetraphenylcyclopentadienone in Experiment [A3J. Tetraphenylcyclopenta-dienone is then converted to hexaphenylbenzene in Experiment [A4ab]. 

Benzil also has a characteristic UV spectrum (see Fig. 7.2). It exhibits a wavelength maximum (Xmax) at 259 nm (smax = 16,329 methanol). It is of interest to compare this absorption spectrum of benzil with that of benzoin (Experiment [Ala]). If the melting point and infrared spectrum compare reasonably closely to the literature values, this material may be used in the synthesis of tetraphenylcyclopentadienone (Experiment [A3a]). If the melting point is low, check the product s purity by thin-layer chromatography. 

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