2.2.2- Trichloro-1,1 -dimethyl group

An acid-catalyzed substitution of a 6-oxo group on 2-aminopteridine-4,6-dione with hydrogen chloride in alcohols (65-100°, 3 hr, 80% yield) represents a convenient synthesis of the 6-alkoxy analogs. The reaction proceeds also with pteridine-2,4,6-trione and its 1-methyl and 1,3-dimethyl derivatives. While methoxylation of 2,4,7-trichloro-quinoline gives about equal amounts of 2- and 4-substitution, acid-catalyzed hydrolysis gives specific reaction at the 2-position only. ... 

A new type of asymmetric hydrosilylation which produces axially chiral allenylsilanes has been reported by use of a palladium catalyst coordinated with the bisPPFOMe ligand 51b.64 The hydrosilylation of l-buten-3-ynes substituted with bulky groups such as tert-butyl at the acetylene terminus took place in a 1,4-fashion to give allenyl(trichloro)-silanes with high selectivity. The highest enantioselectivity (90% ee) was observed in the reaction of 5,5-dimethyl-T hexen-3-yne with trichlorosilane catalyzed by the bisPPFOMe-palladium complex (Scheme 13). 

The trichloromethyl group in s-triazines is sufficiently reactive to he displaced by ammonia, amines, or alkoxides even if two deactivating groups have already been introduced. In contrast, under much more vigorous conditions benzotrichloride and 2,6-bis(trichloro-methyl)pyridine are unreactive towards ammonia in dimethyl-formamide (2 hr, 165°). Tris-amination of 2,4,6-tris-(trichloro-methyl)-s-triazine is complete in aprotic, but not in protic, solvents. 

In the group of phosphonic acid derivatives, 0,0-dimethyl-(l-hydroxy-2,2,2-trichloro)ethane phosphonate, known under the name trichlorfon (Dipterex , 68), occupies a special place both chemically and biologically. It is prepared by the addition of dimethyl phosphonate to chloral (Barthel et al., 1954 Lorenz, 1953a). 

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