Birch-Hiickel Reduction

Polyfullerenes C qH with n reaching from 18 to 44 were observed imder Birch conditions (for n 44 see Section 5.3.4). Isomers with more than 36 hydrogens could not be obtained with the usual Birch procedure. Much milder conditions were necessary and were found with the Benkeser reduction [43]. CgoHjg, obtained with Birch reduction, was subjected to a reduction with li in refluxing ethylene-diamine and yielded four new polyhydrofullerenes, C qH with n = 38, 40, 42 and 44 [43]. These derivatives could be separated by preparative HPLC and characterized by mass spectrometry. 

Under exclusion of light and air C5QH35 has good stability towards high temperature [55]. Nevertheless, extended heat treatment of the polyhydrofullerene mixture leads to an increasing peak of Cg H g. Indeed, CggH g formation can predominate if the reaction is carried out at high temperature and pressure [58]. 

Since deuterochloric acid DCl is easily available, the reduction with Zn and cone. 

C70 is less reactive in terms of hydrogenation than CgQ. Zn-HCl reduction was complete after 1.5 h and gave a pale yellow product, consisting of C7QH35 and C oHjg as major products and as further products [55]. Deuteration of shows 

The predominance C5QH35 and CggHjg formation under the applied conditions has been conclusively proven via He NMR [48, 52], NMR and NMR [51, 61, 

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Compared with the Birch-Hiickel reduction of Cjq, transfer hydrogenation produces less isomers. As well as mainly and CggHjg, in good yields, a... 

This reaction was first reported by Wooster in 1937d and subsequently by Hiickel et al in 1939, for the reduction of aromatic compounds by sodium in liquid ammonia with water however, no structural information was provided. It was Birch who extended Wooster s protocol in 1944 and since then had extensively explored the reduction of benzene and aromatic derivatives with alkali metal (i. e Li, Na, K) in liquid ammonia in the presence of an alcohol (as the proton donor) to produce corresponding cyclohexa-1,4-diene derivatives." Therefore, the reduction of aromatic compounds by alkali metal in liquid ammonia in the presence of alcohol is generally known as the Birch reduction or metal-ammonia reduction. In addition, this reaction is also referred to as the Birch reaction, and in one instance is cited as the Birch-Hiickel reduction. ... 

The procedure described for the Birch reduction of naphthalene is a modification of the methods previously developed by Birch,5 Hiickel,2 and Grob.6 Apart from this reduction, no other practical approaches to isotetralin have become known. The scale employed in the present procedure is not mandatory to achieve optimum yields. Equally good yields were realized when the runs were halved or enlarged up to fourfold. In the latter case, however, the apparatus already reaches pilot plant dimensions. 

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