2,2-Binaphthyl

Crown compounds containing a single 2,2 -binaphthyl subunit.116... 

Table 3.20. Crown compounds containing two 2,2 -binaphthyl subunits...

Lehn and his coworkers have prepared a number of chiral cryptands based upon the 2,2 -binaphthyl unit " . In a typical preparation, the binaphthyl units are treated with bromoacetic acid to form the phenoxyacetic acid derivatives which are then converted into the corresponding diacyl chlorides (75). Reaction of 15 with l,10-diaza-18-... 

If a bridged bis-crown is used instead of diaza-18-crown-6, the cryptand contains two macrorings facing each other (see Table 8.5). Note also that the 2,2 -binaphthyl unit has been used extensively by Cram and his coworkers to provide chirality to mono-cyclic systems as well (see Sect. 3.13). 

With 2,2 -binaphthyl-3,3 -dicarbaldehyde, however, nitrogen elimination is again observed and only pentaphene is obtained.21... 

Now the interesting question arose of whether the intermediate analogous to 215 but devoid of the methyl groups, that is, 3d2-l H-naphthalene (221), would also be interceptable, because 221 should show a high thermodynamic acidity owing to its conversion into the 2-naphthyl anion (224) on deprotonation and because of the use of the strong base KOtBu for the liberation of 221 from 3-bromo-l, 2-dihydro-naphthalene (220) (Scheme 6.52). In the event, the major product was indeed naphthalene. However, there were further products, namely the enol ether 223 and small quantities of 2,2 -binaphthyl (228) as well as 1,2-dihydronaphthalene (226). The overall yield amounted to 92% [137]. 

The use of vinyl epoxides as substrates in enantioselective copper-catalyzed reactions, on the other hand, has met with more success. An interesting chiral ligand effect on Cu(OTf)2-catalyzed reactions between cyclic vinyloxiranes and dialkylzinc reagents was noted by Feringa et al. [51]. The 2,2 -binaphthyl phosphorus amidite ligands 32 and 43 (Fig. 8.5), which have been successfully used in copper-catalyzed enantioselective conjugate additions to enones [37], allowed kinetic resolution of racemic cyclic vinyloxiranes (Scheme 8.26). 

Binaphthyl is obtained by submitting 2-naphthylteUurium trichloride to a similar treatment. ... 

The only examples of carbocyclic products arising from cyclizations subsequent to Srn 1 reactions, are the isolated example reported by Bunnett and Singh,94 which gives products (18H20 Section 2.2.2.4.2) and the recently reported synthesis of unsymmetrically hydroxylated 2,2 -binaphthyls.114 The final pro-... 

Crabtree and Chianese have extended the scope of Hoveyda s ligand by making the imidazolium salt 39 in two steps from l,l/-diamino-2,2/-binaphthyl (Fig. 10) [80]. They prepared neutral rhodium and iridium complexes with that ligand precursor and applied these complexes in the asymmetric hydrosilylation of acetophenone. Moderate enantioselectivities were obtained with the iridium derivative (up to 60% ee) whilst the rhodium catalysts only gave low enantioselectivities. 

Auch Natrium in 1,2-Dimethoxy-athan ist zur Diarylather-Spaltung geeignet. Z. B. erhalt man aus DinaphthyI-(2)-ather ein Gemisch aus 2-Naphthol (F 122°), Naphthalin (F 80-83°) und 2,2 -Binaphthyl (F 181-183,5°)5. 

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