Lithium naphthols

A biexponential decay was observed in weakly polar solvents like dioxane, THF or dimethoxyethane CIP and SSIP ion pairs coexist in these solvents with a majority of CIP in the case of lithium naphtholate while the SSIP dominates in the case of the potassium salt. In the presence of a crown ether and sodium cation, a monoexponential decay was observed and this allowed the attribution of the longest decay time to the SSIP. 

Kobayashi et al. have reported the use of a chiral lanthanide(III) catalyst for the Diels-Alder reaction [51] (Scheme 1.63, Table 1.26). Catalyst 33 was prepared from bi-naphthol, lanthanide triflate, and ds-l,2,6-trimethylpiperidine (Scheme 1.62). When the chiral catalyst prepared from ytterbium triflate (Yb(OTf)3) and the lithium or sodium salt of binaphthol was used, less than 10% ee was obtained, so the amine exerts a great effect on the enantioselectivity. After extensive screening of amines, ds-1,2,6-... 

As previously described, a mixture of and J -octalins can be prepared by the reduction of naphthalene or Tetralin. Another route to this mixture is the dehydration of a mixture of 2-decalol isomers. This latter route has certain advantages in that one can avoid the handling of lithium metal and low-boiling amines. Moreover, 2-decalol is available commercially or can be prepared by the hydrogenation of 2-naphthol (5). In either case a comparable mixture of octalins is obtained, which can be purified by selective hydroboration to give the pure J -octalin (Chapter 4, Section III). 

The reaction between epoxides and ammonia is a general and useful method for the preparation of P-hydroxyamines. " Ammonia gives largely the primary amine, but also some secondary and tertiary amines. The useful solvents, the ethanolamines, are prepared by this reaction. For another way of accomplishing this conversion, see 10-54. The reaction can be catalyzed with Yb(OTf)3 and in the presence of a-BINOL is l,l -bi-2-naphthol derivative gives amino alcohols with high asymmetric induction. A variation used Yb(OTf)3 at lOkbar or at ambient pressure. Lithium triflate can also be used. Primary and secondary amines give, respectively, secondary and tertiary amines, for example. 

A 3-1. three-necked flask, equipped with a Dry Ice condenser (Note 1), a sealed Hershberg-type stirrer, and an inlet tube, is set up in a hood and charged with 108 g. (0.75 mole) of a-naphthol (Note 2). The stirrer is started, and to the rapidly stirred flask contents (Note 3) is added 11. of liquid ammonia as rapidly as possible (about 5 minutes). When the naphthol has gone into solution (about 10 minutes), 20.8 g. (3.0 g. atoms) of lithium metal (Note 4) is added in small pieces and at such a rate as to prevent the ammonia from refluxing too violently (Note 5). After the addition of the lithium has been completed (about 45 minutes), the solution is stirred for an additional 20 minutes and is then treated with 170 ml. (3.0 moles) of absolute ethanol which is added dropwise over a period of 30-45 minutes (Note 6). The condenser is removed, stirring is continued, and the ammonia is evaporated in a stream of air introduced through the inlet tube. The residue is dissolved in 1 1. of water, and, after the solution has been extracted with two 100-ml. portions of ether, it is carefully acidified with concentrated hydrochloric acid. The product formed is taken into ether with three 250-ml. extractions, and then the ether extract is washed with water and dried over anhydrous sodium sulfate. The ether is removed... 

Tertiary and aromatic nitroso compounds are not readily accessible consequently not many reductions have been tried. Nitrosobenzene was converted to azobenzene by lithium aluminum hydride (yield 69%) [592], and o-nitrosobiphenyl to carbazole, probably via a hydroxylamino intermediate, by treatment with triphenylphosphine or triethyl phosphite (yields 69% and 76%, respectively) [298]. Nitrosothymol was transformed to amino-thymol with ammonium sulfide (yield 73-80%) [245], and a-nitroso-/J-naphthol to a-amino-/J-naphthol with sodium hydrosulfite (yield 66-74%) [255]. 

Similarly, lithium aluminum hydride gives different products. / -Naphthyl p-toluenesulfonate affords p-thiocresol and ) -naphthol, and phenyl meth-anesulfonate gives methyl mercaptan and phenol. On the other hand, propyl p-toluenesulfonate yields />-toluenesulfonic acid and propane, and cetyl meth-anesulfonate and cetyl p-toluenesulfonate give hexadecane in 92% and 96% yields, respectively [680]. 

B. A 500-mL, two-necked, round-bottomed flask is equipped with a Teflon-coated magnetic stirring bar (Note 1), condenser, rubber septum and nitrogen inlet. The flask is charged with a suspension of lithium aluminum hydride (UAIH4) powder (2.13 g, 53.4 mmol) in 110 mL of anhydrous THF. The suspension is stirred at room temperature and a solution of ethanol (EtOH) (3.13 mL, 53.4 mmol, Note 7) in 10 mL of THF is added dropwise over a period of 15 min with vigorous evolution of hydrogen gas. The mixture is stirred for 20 min and a solution of (R)-1,1 -bi-2-naphthol (16.0 g,... 

Phenol annelation.1 This modified methyl vinyl ketone can be used for synthesis of 5,6,7,8-tetrahydro-2-naphthol or 5-indanol by reaction with the lithium enolate of cyclohexanone or cyclopentanone, respectively. The former reaction is formulated in equation (I). 

In a recent paper, Soumillion and co-workers [49] were able to identify CIP and SSIPin the P-naphtholate anion/alkali cation/tetrahydrofuran system. They found out that with lithium, a CIP is formed whereas with sodium/crown ether, a SSIP results. Using uncomplexed sodium or potassium counterion, mixtures of CIPs and SSIP s were detected. All their conclusions are based on spectral shifts in the transient absorption and emission spectra which were gained using laser flash spectroscopy. 

In 1979, Noyori and co-workers invented a new type of chiral aluminum hydride reagent (1), which is prepared in situ from LiAlEE, (S)-l, E-bi-2-naphthol (BINOL), and ethanol. The reagent, called binaphthol-modified lithium aluminum hydride (BINAL-H), affects asymmetric reduction of a variety of phenyl alkyl ketones to produce the alcohols 2 with very high to perfect levels of enantioselectivity when the alkyl groups are methyl or primary1 (Scheme 4.3a). 

Naphthols are reduced to P-tetralones (which are presumably protected from further reaction as the corresponding enolate anions) even more readily and it is surprising to find that even 6-methoxy-2-naph-thol (65) is converted into ketone (66 Scheme 11). ° Reduction of the equilenin ketal (67) was found to be highly dependent on the choice of metal. Reduction of (67 Scheme 12) or its sodium salt by lithium in the absence of an alcohol afforded (after acid hydrolysis) equilin (68) as the major product, whereas... 

Deoxygenation of phenols may be achieved by reduction of aryl diethyl phosphates with lithium or sodium in liquid ammonia." A recent application of the methodology is outlined in Scheme 43." The reaction works well with a variety of substituted phenols, but not with dihydric phenols or naphthols. The alternative reduction of aryl sulfonates has also been examined, but the limited solubility of these derivatives can present difficulties. 

By derivatizing an a,p-unsaturated acid into the mono ester of chiral 1,1 -bi-8,8 -naphthol the reaction with lithium dialkylcuprates leads to saturated ketones containing chirality centers at the p-carbon atoms." Consecutive 1,4-addition and 1,2-addition account for this result. The alkyl transfer to enones from Grignard reagents under copper catalysis is subject to chiral modification, e.g., by the introduction of 56" or 57." ... 

Wittig and Pohmer prepared this reagent by shaking a solution of o-fluorobromo-benzene in furane with lithium amalgam for four days they found that it is cleaved by mineral acid to a-naphthol. In a simpler route to the reagent described by Fieser... 

---