Introduction of other functional groups

Similar halogenations have been done on 2-lithio-l-phenylsulfonylindole[2], 2-Lithio-l-phenylsulfonylindole is readily converted to the 2-(trimethylsilyl) derivative[2,3]. 2-Trialkylstannylindoles can also be prepared via 2-lithio-indoles[4,5], 2-Sulfonamido groups can be introduced by reaction of a 2-lithioindole with sulfur dioxide, followed by conversion of the sulfinic acid group to the sulfonyl chloride with A-chlorosuccinimide[6]. 

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The introduction of other functional groups into the oxadiazole nucleus by nucleophilic substitution of substituted 1,3,4-oxadiazoles is also difficult (cf. Section III,B). The few known examples proceed with low yield.1 Thus 2-phenyl-5-amino-l,3,4-oxadiazole is obtained by ammonolysis of 2-phenyl-5-methanesulfonyl-l,3,4-oxadiazole [Eq. (9)]-96... 

The nitrocalixarenes provide extremely useful intermediates for the introduction of other functional groups, generally via the amino calixarenes obtained by reduction with H2 and Raney NH2NH2 and Raney Ni, ° NH2NH2 and... 

In cases where either the polyamine moiety differs distinctly from the commercially available building blocks or polyamines with more diversity are required, the backbone is preferentially generated by stepwise and modular elongation. Diversity can be achieved by the introduction of different aliphatic chains between the nitrogens, branching of the skeleton in aUcyl-or amino position, and the introduction of other functional groups into the backbone. This finally opens access to numerous compounds that are different in detail but structurally closely related. 

The favorable order of selectivity achieved by the dlmethoxyphosphlnothloyl derivatives prompted the examination of other functional groups for Introduction of the "delay factor"... 

Silanes with functional groups like amino, cyano, flonr, phenyl, etc. are available commercially. The introduction of other functional gronps in the bonded moiety can be accomplished in two ways The silane with the functional gronp is prepared in sitn. To prepare a silane with an amide group, tri-alkoxy-3-aminopropyl silane is reacted with an acid chloride (C8 or C18). The thns prepared amide... 

The only other group of compounds that has exhibited unusual reactions is the thieno[3,4-, pyridazines. The types of reaction involve either ring expansion (or addition) and introduction of a functional group onto the ring. 

The introduction of chelating functional groups (e.g. amino diacetate) into polymer beads yields a product with a high affinity for metal ions, but also capable of excluding large molecules and colloidal particles from the inner pores (i.e. in some situations the column can act as a size differentiation medium) (Florence, 1977). Compared with other techniques (such as dialysis, ultra-filtration and solvent extraction), chelating column separations can be claimed to be faster and simpler, with the equipment being relatively less expensive. 

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