2- phenyl-, ring synthesis

The first synthesis of amphiphilic porphyrin molecules involved replacement of the phenyl rings in TPP with pyridine rings, quaternized with C2QH 2Br to produce tetra(3-eicosylpyridinium)porphyrin bromide (3) (36). The pyridinium nitrogen is highly hydrophilic the long C2Q hydrocarbon serves as the hydrophobic part. Tetra[4-oxy(2-docosanoic acid)]phenyl-porphyrin (4) has also been used for films (37). 

An elegant procedure for the synthesis of 5//-dibenz[c,e]azepines 14, which is an extension of the procedure outlined at the beginning of this section, has been developed in which the nitrile ylides, generated by the treatment of iV-(2-arylbenzyl)benzimidoyl chlorides 12 with potassium /er/-butoxide, undergo a 1.7-electrocyclization at the adjacent phenyl ring, followed by a hydrogen shift 13 - 14.102... 

It is worth noting that as early as 1903 Hantzsch felt that the possibility of forming the pentazole ring lay in the phenyl azide synthesis. 

An 8-phenylmenthol ester was employed as the chiral auxiliary to achieve enantioselectivity in the synthesis of prostaglandin precursors.83 The crucial features of the TS are the anti disposition of the Lewis acid relative to the alcohol moiety and a tt stacking with the phenyl ring that provides both stabilization and steric shielding of the a-face. 

A series of similar reactions was examined in the course of synthesis of substituted chromanes.155 The reactions are thought to proceed through TS M in preference to N because of steric interactions with the phenyl ring on the chiral hydroxylamine. 

Similar protocols have been followed for the synthesis of other porphyrin-C6o diads where the linkage between Cm and porphyrin moieties occurs through the ortho, meta or para positions of the phenyl ring of the porphyrin macrocycle <00PP598, 03JPC(A)8834 and 06SC2135>. 

After isolating the product of a solid phase synthesis, the support (resin + linker) is usually discarded as waste, although successful examples of its reuse in further synthetic cycles are known with trityl type linkers (Frechet and Haque 1975). To reduce both volume of operation and amount of waste, the loading of the resin (quantified as millimoles of functionality per gram) has to be increased. Besides theoretical limitations (for polystyrene this is reached when every phenyl ring is substituted by the linker), there may be practical boundaries for using highly loaded resins in solid-phase supported synthesis. This issue was studied... 

Thin polymer films have been prepared by surface catalysis in ultrahigh vacuum and electrochemical deposition from solution. These two routes of synthesis result in poly(thiophene), poly(aniline) and poly(3,5-lutidine) films that have similar infrared spectra. These polymer films are highly orientationally ordered the rings are perpendicular to the surface in poly(thiophene) and poly(3,5-lutidine) films, and the phenyl rings are parallel to the surface in poly(aniline). 

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