Silica sulfuric acid and silica chloride, two silica based solid acids have been used for various organic functional group transformations either as reagent or as catalyst. All reactions have been carried out under mild and heterogeneous conditions. These reagents were used for C-C, C-N, and C-O bond formation and cleavage and also deprotection of different protecting groups. Silica sulfuric acid was recycled in many cases, and reused. Silica chloride has been used as a starting material for preparation of some new silica based reagents with special properties.

This review article summarizes published data on the application of N-halo reagents (such as N-halo amines, N-halo amides and/or imides, N-halo sulfonamides and/or imides, and etc.) in various organic functional group transformations such as: oxidation reactions, deprotection and protection of different functional groups, halogenation of saturated and unsaturated compounds, acylation of alcohols, phenols, amines or thiols, epoxidation of alkenes, aziridination and etc. The main purpose of writing this review is encouraging of active researchers interested to this field for the synthesis of new N-halo reagents specially with different halogens and applications of these new N-halo reagents in organic reactions or finding more and more applications of existing N-halo reagents in organic synthesis.