2- tert-Butylnaphthalene

Regardless of whether the Pd-catalyzed coupling or alkyne metathesis is utilized to make PAEs, the critical step is the synthesis of the diiodoarene monomers. In this section some of the more interesting syntheses are showcased. The synthesis of dipropynyldi-tert-butylnaphthalene is shown in Scheme 5. Starting from naphthalene, Friedel-Crafts alkylation with 2-chloro-2-methylbutane gives a mixture of two di-tert-butylnaphthalenes that are separated by crystallization. Iodination of the correct isomer is followed by a Pd-catalyzed coupling of propyne to the diiodide to give the desired l,5-dipropynyl-3,8-di-tert-butyl-naphthalene [56] ready for ADIMET. 

Following this study, we found that the optimum conditions for maximising the yield while retaining selectivity involved two successive 1 h autoclave reactions at 180 °C, using HM (4.0 g, Si/Al ratio 17.5), /er/-butanol (80 mmol) and cyclohexane (10 ml) for an initial 10 mmol of naphthalene. Under these conditions, a 2,6-di-tert-butylnaphthalene yield of 50 % and a 2,6/2,7 ratio of 58.5 were achieved after the first reaction, and a 60 % yield with a ratio of 50.6 after the second stage. The optimised result is compared with the most selective literature result in Table 4. 

Eight pure liquids (water, methylene iodide, n-hexadecane, formam-ide, hexachloropropylene, tert-butylnaphthalene, dicyclohexyl, and n-decane) were chosen for this investigation, with special emphasis on the data for the first three. 

Properties of the three liquids of special interest are compared in Table I. The liquid surface tension, vlv > these reference liquids covers almost a threefold range at 20°C. In this same range are the surface tensions at 20°C. for the five other freshly purified liquids, formamide, hexachloropropylene, tert-butylnaphthalene, dicyclohexyl, and decane (58.2, 38.1,33.7, 32.8, and 23.9 dynes per cm., respectively). 

In view of the uncertainty regarding the effect of temperature on the benzene result and because the hydrocarbon surfaces of interest are paraffinic rather than aromatic, any estimate for the solid-liquid tension for solid-benzene pairs is less satisfactory than the n-decane value. Nevertheless, it is of interest to make such estimates for several other hydrocarbon liquids as well as for benzene. The increase in solid-liquid interfacial tension for aromatic compoxmds, which is indicated by the undercooling experiments, can at least be reflected in such estimates. Since both one-liquid and two-liquid adhesion tension data are available for isopropylbiphenyl, an estimate for this liquid is desirable. For comparison, and because one-liquid adhesion data exist, tert-butylnaphthalene has been chosen as another case for which an estimate of the solid-liquid interfacial tension has been made. 

These estimates are given in Table IV. Also presented are estimates appropriate to fluorocarbon surfaces. In the latter case, the values for benzene and tert-butylnaphthalene are chosen to correspond with the results obtained by use of the interaction parameter method, as given in Table H. For both the fluorocarbon surfaces and the hydrocarbon surfaces, the estimates given are also in agreement with the differences between the values for n-decane and isopropylbiphenyl, as deduced from two-liquid adhesion tension data. 

In the case of paraffin, no film pressures are available, since two-liquid adhesion tension data are lacking. Thus, it was necessary to assume a film pressure for one of the liquids in contact with paraffin. For this, a value of 1 dyne per cm. was taken as the film pressure of tert-butylnaphthalene. If a higher value had been chosen, the solid-vacuum and solid-liquid water tensions would have been correspondingly higher. Since the interfacial tension with water in this case seems already high, in comparison with liquid-liquid interfacial tensions for paraffin hydrocarbons [23], the quoted film pressure was adopted. 

Bromonaphthalene Tricresyl phosphate Hexachloropropylene 1,1 -Dipheny lethane tert-Butylnaphthalene Dicyclohexyl Bis(2 -ethylhexyl) orthophthalate Squalane Hexadecane Tetradecane... 

As shown in Scheme 1, the synthesis of fert-butyl phenalenyl radical 10 started from 2,7-di-ferf-butylnaphthalene in ten steps. Bromination of 2,1-di-tert-butylnaphthalene gave 6 in high yield, which was converted into aldehyde by lithiation followed by reaction with DMF. Successive Reformatsky reaction afforded ester 7, which upon reduction, hydrolysis, and Friedel-Crafts acylation reaction gave the phenalanone 8. The key intermediate 9 was then obtained as pale yellow crystals by reduction of 8 and subsequent dehydration. Oxidation of 9 with p-chloranil in degassed toluene led to a blue neutral radical solution while similar treatment in hexane gave deep blue needles. This crystal showed high stability in the absence of air, while changing into phenalanone derivatives and other byproducts in 1 week in air. 

Weniger, K. Jost, M. Grutzmacher, H. F. Mass spectrometry of Di-tcrt-butylnaphthalenes and benzyl-tert-butylnaphthalenes Hydrogen Migration and intermediate ion-molecule complexes in ferf-butylated naphthalene ions. Eur. Mass Spectrom. 1999, 5,... 

Franck, R.W., Yanagi, K., 1968. Compression effects in 1,4-di-tert-butylnaphthalenes. Chemistry and nuclear magnetic resonance spectra. Journal of Organic Chemistry 33,811-816. 

The Fajula group also recently studied the alkylation of naphthalene with tert-butanol.57 Over H-beta 2-te/t-butylnaphthalene was obtained as the main product together with relatively small amounts of the di-terr-butylnaphthalenes. Over HY 2,6-and 2,7-di-terf-butylnaphthalene the major products, demonstrating again the more spacious Y-pore system. 

A soln. of 1,3,8-tri-terr-butylnaphthalene in hexane irradiated 48 hrs. with the Pyrex-filtered light of a 450 w. high-pressure Hg-lamp 1,3,9-tert-butyl-... 

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