Ring with phenyl lithium

The cage-like phosphonium salt (17) with phenyl-lithium in THF gave the phosphorane (18) which probably owes its great stability to the relief of strain in the ring structure on changing the bond angle at phosphorus to 90°. For the photolysis of (18) see Chapter 10, Section 1. 

Tetrachloroselenophene undergoes a ring-opening reaction on treatment with phenyllithium initiated by nucleophilic attack on selenium. Further reaction with phenyl-lithium results in the formation of diphenyl selenide (Scheme 11) (76CS(10)133). 

When A.A-dimethylisoindolinium bromide is treated with phenyl-lithium, it gives V-methylisoindole via the ylid (54).2 59,60 An attempt to prepare benzo[c]thiophene via the analogous ylid (55) failed. Thus, when l,3-dihydrobenzo[c]thiophene methylsulfonium iodide was treated with phenyllithium, it gave a mixture of methyl phenyl sulfide, spiro[5.5]-l-methylthio-2,3-benzo-6-methylthio-methyleneundeca-7,9-diene (56), and 3,4-bis(methylthio)-l,2 5,6-dibenzo-l,5-cyclooctadiene (57).59,60 The formation of methyl phenyl sulfide may be explained by the formation and ring cleavage of compound 58, and compounds 56 and 57 arise by Diels-Alder dimerization of the o-quinodimethane (59) formed by ring cleavage of the ylid (55). 

Bromobenzotellurophene did not react with phenyl lithium. Butyl lithium in diethyl ether/hexane cleaved the tellurophene ring, even at — 50°, yielding butyl 2-ethynylphenyl tellurium2. 

Several different synthetic approaches have been used for the synthesis of fluorinated macrocycles. The simplest one relies on the introduction of a fluorinated substituent into hydrocarbon macrocycle. For example, the preparation of dibenzocrown ethers 128 is based on the reaction of the corresponding 4,4 - or 4,5 -diaminodibenzo-18-crown-6 ethers bearing amino groups on the phenyl ring with fluorinated lithium... 

A novel route to cyclopentyne has been developed, allowing ready access to fused five-membered rings. The new method involves treatment of dibromo-methylenecyclobutane (93) with phenyl-lithium, so generating cyclopentyne... 

Spectroscopic investigations of the lithium derivatives of cyclohexanone (V-phenylimine indicate that it exists as a dimer in toluene and that as a better donor solvent, THF, is added, equilibrium with a monomeric structure is established. The monomer is favored at high THF concentrations.110 A crystal structure determination was done on the lithiated A-phenylimine of methyl r-butyl ketone, and it was found to be a dimeric structure with the lithium cation positioned above the nitrogen and closer to the phenyl ring than to the (3-carbon of the imine anion.111 The structure, which indicates substantial ionic character, is shown in Figure 1.6. 

Machiguchi, Nozoe and coworkers have very recently observed that in contrast to chemical reactivity of tropones, the tosylate of tropone oxime undergoes a facile ring-opening to 6-substituted (Z,Z,Z)-1,3,5-hexatriene nitriles on reaction with various nucleophiles305. For example, reaction of phenyl lithium results in the corresponding hexatriene carbonitrile (equation 183). 

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