2-phenylethane-, lithium

This method is very useful for the construction of 1-substituted 3,4-dihydroisoquinolines, which if necessary can be oxidized to isoquinolines. A P-phenylethylamine (l-amino-2-phenylethane) is the starting material, and this is usually preformed by reacting an aromatic aldehyde with nitromethane in the presence of sodium methoxide, and allowing the adduct to eliminate methanol and give a P-nitrostyrene (l-nitro-2-phenylethene) (Scheme 3.17). This product is then reduced to the p-phenylethylamine, commonly by the action of lithium aluminium hydride. Once prepared, the p-phenylethylamine is reacted with an acyl chloride and a base to give the corresponding amide (R = H) and then this is cyclized to a 3,4-dihydro-isoquinoline by treatment with either phosphorus pentoxide or phosphorus oxychloride (Scheme 3.18). Finally, aromatization is accomplished by heating the 3,4-dihydroisoquinoline over palladium on charcoal. 

In the similar structure of l.l,1,2,4,4,4-heptafluoro-3-phenylbut-2-ene, the reduction with sodium borohydride takes place readily under mild conditions and both products of vinylic and allylic Sn2 displacement are obtained the relative amounts of the products can be controlled by adding triphenylphosphane to the mixture80 (Table 2). The nonfluorinated chain in Hpenta-fluorophenyl)-2-phenylethane (12) selectively activates the para C-F bond to reduction by lithium aluminum hydride, giving the monoreduced product 13 in high yield.81... 

Johansson and Davidsson47 have reported on the NMR studies of a mixture of two different chelating lithium amides, one with an ether chelate, derived from (R)-l-methylamino-2-methoxy-l-phenylethane (9), and one with an amine chelate (Li-4). It was found that the Et20 solution contained different dimers, both homo and hetero dimers. Based on NMR data it was concluded that a mixture of the two hetero dimers, both symmetrically ((Li-4/Li-9) 2Et20) and unsymmetrically ((Li-4/Li-9) Et20) solvated, dominated in solution. 

Methylene compounds with two neighboring sulfone groups can also be used for diazo transfer reactions as shown in 1964 by Klages and Bott. They obtained diazobis(ethylsulfonyl)methane (2.127) and diazobis[(diethylamino)sulfonyl)]me-thane (2.128) in aqueous ethanol and NaOH at - 5 °C and in ether with methyl-lithium at room temperature, respectively. In a similar way, methylene compounds activated by a sulfone and a carbonyl group, yield diazo derivatives, e.g., 1-diazo-l-(4 -toluene)sulfonyl propan-2-one (2.129, van Leusen et al., 1965), 2-diazo-2-(me-thylsulfonyl)-2-phenylethan-l-one (2.130, Illger et al., 1972), l-diazo-l-[(4 -nitro-phenyl)sulfonyl)]propan-2-one (2.131, Hodson et al., 1968), and other a-diazo-)ff-oxo-)ff -sulfonyl compounds (Monteiro, 1987 b) and similar diazoalkanes (van Leusen and Strating, 1988). 

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