CA-Decalin

Early pulse radiolysis studies of alkanes at room temperature showed that the solvated electron absorption begins around 1 pm and increases with increasing wavelength to 1.6 pm for -hexane, cyclohexane, and 2-methylbutane [77]. More complete spectra for three liquid alkanes are shown in Fig. 4. The spectrum for methylcyclohexane at 295 K extends to 4 pm and shows a peak at 3.25 pm [78]. At the maximum, the extinction coefScient is 2.8 x 10 cm The spectrum for 3-methyloctane at 127 K, shown in Fig. 4, peaks around 2 pm. The peak for methylcyclohexane is also at 2 pm at lower temperature. Recently, the absorption spectra of solvated electrons in 2-methylpentane, 3-methylpentane, cA-decalin, and methylcyclohexane glasses have been measured accurately at 77 K [80]. For these alkanes, the maxima occur at 1.8 pm, where the extinction coefScient is 2.7 x 10 cm. ... 

Naphthol 1 cA-decalin (12), 1-hydroxy decalin (37), trans- 1-decalone (51)... 

Asymmetric cyclization using chiral ligands offers powerful synthetic methods for the preparation of optically active compounds [39]. After early attempts [40,41], satisfactory optical yields have been obtained in a number of cases. Synthesis of the optically active cA-decalin system [42] was carried out with high enantioselectivity based on the differentiation of enantiotopic C=C double bonds [43]. The cyclization of the triflate 93 gave the cA-decalin 94 with 95% ee in 78% yield using (i )-BINAP. A mixture of 1,2-dichloroethane and f-BuOH is the best solvent, and the asymmetric synthesis of vemolepin (96) via Danishefsky s key intermediate 95 has been achieved [44]. 

Usually o.v-dccalin is formed more selectively from tetralin than from naphthalene. Baker and Schuetz obtained a mixture of 77% cis- and 23% frans-decalin in the hydrogenation of naphthalene over Adams platinum oxide in acetic acid-ether at 25°C and 12.8 MPa H2, while cA-decalin was obtained exclusively in the hydrogenation of tetralin in acetic acid under similar conditions.23... 

A high degree of stereoselectivity can be achieved in chelation-controlled reactions, utilizing hydroxy groups as stereodirectors (Eq. 59) [69], Studies have revealed that non-chelation-controlled processes may also proceed with enhanced selectivities, and this led to the synthesis of the cA-decalin skeleton of vinigrol (Eq. 60) [70]. 

Among the most important of the bicyclic hydrocarbons are the two stereoisomeric bicyclo[4.4.0]decanes, called cis- and franx-decalin. The hydrogen snbstitnents at the ring junction positions are on the same side in cA-decalin and on opposite sides in trans-decalin. Both rings adopt the chair conformation in each stereoisomer. 

Decalin ring systems appear as structural units in a large number of naturally occurring substances, particularly the steroids. Cholic acid, for example, a steroid present in bile that promotes digestion, incorporates cA-decalin and franx-decalin units into a rather complex tetracyclic structure. 

Fig. 4, peaks around 2 pm. The peak for methylcyclohexane is also at 2 pm at lower temperature. Recently, the absorption spectra of solvated electrons in 2-methylpentane, 3-methylpentane, cA-decalin, and methylcyclohexane glasses have been measured accurately at 77 K [80]. For these alkanes, the maxima occur at 1.8 pm, where the extinction... 

The same Suzuki methodology was used to synthesize a similar copolymer 446 [548], The polymer showed a solvent-dependent green-yellow emission (from 545 nm in THF to 565 nm in chloroform) as often observed for polar chromophores. The PL QE also varied with the solvent (from 11% in THF to 21% in decalin) but, in contrast to copolymer 445, no strong decrease in emission efficiency was observed in the solid state (4>p1 n= 13%) that could be attributed to the effects of substituents at the thiophene ring. LEDs based on 446 showed, for an ITO/PEDOT/446/Ca/Al architecture, a turn-on voltage of ca. 10 V with a maximum brightness of 340cd/m2 at 22 V and appreciable el = 0.14%. 

The results are not particularly consistent here either. This last reaction, exothermic by ca —206 kJmol-1, is not consistent with either result in equation 43. We strongly doubt the principal source of error is the difference of choice of phases employed57. The difference of the hexahydrotriazine enthalpies of formation, —18 — (—132) = 114 kJmol-1, is comparable to three times the difference of liquid pyrrolidine and piperidine, 132 kJ mol-1. (The difference for other pairs of corresponding 5- and 6-membered ring species includes 166 kJ mol-1 for cyclopentane and cyclohexane, and 162 for perhydroindene and decalin.) The origin of the ca 20 and 50 kJmol-1 discrepancies remains enigmatic. 

R. L. Wilier, Synthesis of a New Energetic Material, 1,4,5,8-Tetranitro-l,4,5,8-tetraazad-ifurano[3,4-c][3,4-h]decalin (CL-15) , NWCTP 6397 (1982), Naval Weapons Center, China Lake, CA. 

Hydrolysis of the enamine 14 furnishes citronellal (15) in high optical purity (ca. 99% ee) which gives 17 via ene cyclization with zinc bromide as catalyst. The diastereoselectivity of this step is the result of simple diastereoselection in a trans-decalin-like transition state 16. Catalytic hydrogenation converts the olefin 17 into (—)-menthol (18). Despite its elegance this novel route has not been able to replace the older resolution-based procedure described earlier in this section. 

To the sodium cycloalkane- or -arenethiolate (20 mmol), preferably freshly prepared from the respective thiol with NaH in THF, in 1.3-dimethylimidazolidin-2-one (DMEU) (15 mL) flushed with N2 or argon was added perfluorinated Decalin (0.5 mmol). The mixture was stirred at ca. 65 C for the indicated time, then poured into toluene (50 mL) and washed with H20 (10x 300mL). The organic phase was dried (Na2S04) and the solvent evaporated. The crude residue was dissolved in CHC12 and purified by preparative TLC (silica gel, CHCl3/hexane 3 1). 

The first samples examined were prepared by the method developed by Smith et al. [70, 71] and by Matsuo [72]. Sample films of a thickness of ca. 100 pm were obtained by drying a gel which was obtained by quenching a 0.4 g/dl decalin solution of linear polyethylene with a molecular weight of 3 x 106 from 140 °C in ice-water. The samples thus obtained could be drawn to a very high extent because of very few intermolecular chain entanglements. However, since they could not be drawn highly in one step, they were drawn 10 times at the first step in a silicon oil bath at 145 °C at a rate of 1.6 times/min and then at the second step they were drawn so that the final draw ratio was 50,100, and 150 times. 

In order to obtain high enantioselectivities it seems to be important that the reactions proceed via cationic intermediates (e.g. 24) to disfavor the partial dissociation of the chiral ligand. For this reason, silver salts are added to reactions of vinyl-iodides. These reactions are best performed in Al-methylpyrrolidone (NMP) as a solvent. As the examples shown in Scheme 9 demonstrate, both c/s-decalin [12] and cA-hydrindane [13] derivatives can be obtained in useful yields and enantiomeric purities. 

The first experimental determination of the inversion barrier of a tertiary arsine was reported in 1971 ". The kinetics of racemization of (/ )-(—)- and (S)-( + )-ll, resolved by the metal complexation method, at 217.6 +0.3 °C in decalin (sealed tube) was determined polarimetrically in the 310-350 nm region. From the kinetic data, by substitution into the Eyring equation, the free energy of activation, AG was calculated to be 175 + 2kJmol at 217.6°C. This energy value corresponds to a half-life for racemization of the arsine of ca 740 h at 200 °C. It had been reported previously that resolved ethylmethylphenylarsine and methyl(n-propyl)phenylarsine showed no detectable loss of optical activity over 10 h at 200 On the basis of photoracemization studies... 

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