2,2 -dilithio

Metallation of 4,4 -, 5,5 -, 6,6 -, and 7,7 -dibenzo[6]thienyl with two molar equivalents of n-butyllithium affords the corresponding 2,2 -dilithio compounds, which give the corresponding 2,2 -dicarb-oxylic acids on carbonation.517... 

Of special interest with respect to the stereochemical questions was the yellow spirophosphorane 31 since according to the new synthetic procedure it could formally be obtained by two ways, either from the tosylimine of 5-phenyldibenzo-phosphole and 4,4 -bis(dimethylamino)-2,2 -dilithiobiphenyl or, the other way round, from 3,7-bis(dimethylamino)-5-phenyldibenzophosphole tosylimine and 2,2 -dilithio-biphenyl. 

Attempts to synthesize by analogous procedures bis-2,2 -biphenylylenemethylstibo-rane (157) from 2,2 -biphenylylenemethylstibine dibromide 154 and 2,2 -dilithio-biphenyl failed, because of the obvious instability of the initially formed stibonium structure 155 which readily loses methyl bromide. The carbanionic stibine 156 so... 

The only compound so far known containing a 1,3-azaborolidine ring is 9-mesityl-97/-pyrrolo[l,2- ][l,3]benzaza-borole 23 <1999JCM264>. This compound was synthesized by treatment of l-(2-bromophenyl)-l/7-pyrrole 54 with -butyllithium in ether to give 2,2 -dilithio-l-phenylpyrrole 55, which was subsequently reacted with dimethoxy-mesitylborane to afford 23 in 76% yield (Scheme 7). 

The reaction of 2,2 -dilithio-l,l -biiu hlhyl with RASCI2 (R=Me or Ph) provided the corresponding (+)-7-R-ditiaphtho[2,1 -fe 1, 2 -d]arsoles [ (6)]. The molecules are fluxional in solution with barriers between the conformational isomers (atropisomers) of 6S 1 (R=Me) and 60 1 kcal mof (R=Ph). An X-ray diffiaction study of [(5 - (6, R=Ph)], vdiich crystallized out by spontaneous resolution, revealed appreciable bending of the distorted luqshthyl residues away from each other. ... 

It appears remarkable that benzylic and poly(p-phenylene diselenide polymers are able to incorporate additional selenium atoms in to the chain through a simple melt alloying process, thus giving products whose structures are intermediate between organic and inorganic polymers [224,227]. Recently, poly(l,l -binaphthyl-2,2 -diselenide) was prepared along with other compounds when 2,2 -dilithio-l,l binaphthyl was reacted with selenium followed by aerial oxidation [228]. 

Many attempts were made to access optically active tetraphenylenes in past years owing to their unique structures and properties. In 2000, Rajca et al. [44] reported that a CuBr2-mediated oxidation coupling of partially resolved (/ )-2,2 -dibromo-l,l -binaphthyl 89 afforded R)-90 in 20% yield with 95% ee (Scheme 5.18). This method was based on the configurational stability of 2,2 -dilithio-l,l -binaphthyl. Amplification of the enantiomeric excess was also observed. Interestingly, when ( )-89 was used under the same condition, ( )-90 was isolated in only a trace amount. 

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