Tetracyclone synthesis

D. Miscellaneous.—A further study of the reactions of diphenyl-phosphine oxide with tetracyclone has confirmed that the reaction yields the oxide (30) under mild, basic conditions, and that the reaction is thermally reversible. The displacement of halogen from phosphorus by amino-compounds has been used in the synthesis of a number of aminofluoro-phosphine oxides (31), and of A-methyl-AA-bis(dichlorophosphinyl)-amine (32). ... 

A further method for the synthesis of o-diaroylbenzenes has been described by Ried and Bdnninghausen. Tetracyclone (145), a potent diene for Diels-Alder reactions, together with dibenzoylacetylene (146) gives 147. This method has proved of value in a number of other cases and is also applicable when the cyclopentadienone derivative is dimeric ° as in the case of 2,5-dialkyl-3,4-diarylcyclopentadienones. °... 

In the synthesis of the bisdienophilic phthalocyanine 102, a Diels-Alder reaction of a reactive isobenzofuran (generated by the tetracyclone route) is involved (97CB801). For further work see [95JCS(CC)2449 98ZN(B)1069],... 

Simple bond energy calculations show that 2H- 1,2-oxazines and -thiazines are unstable relative to the corresponding open chain iminoaldehydes and iminothioaldehydes, and thus they only find expression in the form of transient species. Early claims for the synthesis of 2H- 1,2-oxazines have not been authenticated, and, for example, the reaction between 4-nitrosodimethylaniline and tetracyclone does not give the oxazine (1) as was once thought, but rather the isomeric lactam (2), although it is likely that the oxazine is formed as an intermediate (Scheme 1) (64TL1569). 

The disconnection of both carbon-carbon double bonds in tetraphenylcyclo-pentadienone (14) ( tetracyclone ), in the manner of the examples above, leads to recognition of benzil and dibenzyl ketone as the reagents for its synthesis. 

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). 

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. 

The synthesis of various tetracyclones was reported using PTC under sonication (Eq. 14).55 Instead of refluxing ethanol, toluene at room temperature is a more appropriate medium. A similar crotonization reaction was effected in the presence of basic alumina on the 1/4 molar scale.56 No PTC is needed. 

The dienophilicity of thiet 1,1-dioxide was utilized to synthesize (73) from tetracyclone, whilst it acted also as a good dipolarophile towards diazoalkanes, giving mixtures of 1-pyrazoline derivatives (74) and (75) in which the isomers (74) predominated, except in the cases of diazomethane and diazoethane, where (75) was the major isomer. Ethyl diazoacetate on the other hand gave the 2-pyrazoline (76). These compounds arc potentially useful for the synthesis of bicyclobutanes by sequential expulsion of nitrogen and sulphur, and thermolysis or photol3rsis of (74 = R =... 

Similarly, Diels-Alder/retro-Diels-Alder sequence was utilized to the synthesis of ethyl 4-(trifluoromethyl)furan-3-carboxylate 92 starting from furan and ethyl trifluorobut-2-ynoate via intermediate products 90 and 91 [78], Cycloadduct 90 was also transformed into 92 by two-step procedure including its Diels-Alder reaction with tetracyclone and thermolysis of adduct 93 [79]. 

The complexes (CXVI) are analogous to the derivatives (CIV) discussed in Section V, B. The tetraphenyl derivative (CXVI. 1) gives the tetracyclone-Fe(CO)3 complex (CXIII.l) upon bromination and with methanolic NaOH yields tetraphenylbutadiene-Fe(CO)3 (38, 39, 128). Reaction of this tetraphenyl derivative with appropriate reagents has provided a novel synthesis of furans, thiophenes, selenophenes, pyrroles, phospholes, and arsoles (38, 78, 128). 

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