Peripherally Substituted Octa alkoxymethyl phthalocyanine

The synthesis of non-peripherally substituted octa(alkoxymethyl)phthalocyanines is outlined in Seheme 57 [213, 214]. 2,5-fcij(Alkoxymethyl)furan can be prepared by lithiation of furan followed by quenching the anion with (bromomethyl)alkyl ether to give the mono-substituted furan, and repetition of the procedure to give the required product [213]. A more simple synthesis involves chlorination of 2,5-furan dimethanol with thionyl chloride, followed by nucleophilic displacement of chloride with sodium alkoxide [214]. The furan is equilibrated with fumaronitrile for about a week and the Diels-Alder adduct aromatized by treatment with lithium fcwftrimethylsilyl)-amide (a non-nucleophilic base), followed by an acidic work-up. The 3,6-/7i5(alkoxy-methyl)phthalonitrile is cyclized under standard conditions (lithium/pentanol). 

Scheme 57. Synthesis of non-peripherally substituted octa(alkoxymethyl)phthalocyanines [214]. Reagents (a) SOCI2, (b) RONa/ROH, 36-78% over two steps (c) BuLi (d) ROCHjBr, 20% overall (Cg) (e) fumaronitrile (f) LiN(SiMe3)2/THF (g) H, 4-23% (h) ROLi/ROH, A (i) H 7-34% (j) M acetate, 72-87%.

Table 51. Transition temperatures for non-peripherally substituted octa(alkoxymethyl)phthalocyanines (ROCH2-) (see Scheme 57 for structures).

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