N halogenation

In the preceding parts of Section 4.04.2.1.3 the electrophilic attack on pyrazolic nitrogen with the concomitant formation of different classes of N—R bond has been examined N—H (iv, v), N—metal (vi), N—C(sp ) (vii, viii, xi), N—C(sp ) (be, x, xi), N—SO2R (x), N—halogen (xii), N—O (xiii) and N—-N (xiv). In this last part the reaction with other Lewis acids leading to the formation of pyrazole N—metalloid bonds will be discussed, and the study of their reactivity will be dealt with in Section 4.04.2.3.lO(viii). 

A,V,V-trifliioroalkylamidines N-halogen compounds N-metal derivatives Nitroalkanes, c-nitro, and polynitroaryl compounds... 

It will be convenient to describe first the binary. sulfur nitrides SjN,. and then the related cationic and anionic species, S,Nv. The sulfur imides and other cyclic S-N compounds will then be discus.sed and this will be followed by sections on S-N-halogen and S-N-O compounds. Several compounds which feature i.solated S<—N, S-N, S = N and S=N bonds have already been mentioned in the. section on SF4 e.g. F4S NC,H, F5S-NF2. F2S = NCF3, and FiS=N (p. 687). Flowever. many SN compounds do not lend themselves to simple bond diagrams, - and formal oxidation states are often unhelpful or even misleading. 

Phenyl-[3- (bzw. -4)-chIor-benzyl]- 569 Phenyl-[3- (bzw. -4)-cyan-benzyI]- 569 Phenyl-(n-halogen-benzyl)-. 569 Phenyl-[a-haIogen-3- (bzw. -4)-chlor-benzyI] 569 Phenyl-[a-halogcn-3- (bzw. -4)-cyan-benzyl]-569 Phenyl-(a-halogen-4-nitro-benzyI)- 569 PhenyI-(4-nitro-benzyI)- 569 (1,2,2-TriphenyI-vinyI)-phenyl - 464 Vinyl-phenyl- 633f. 

The reactions in this chapter are classified according to the attacking atom of the nucleophile in the order O, S, N, halogen, H, C. For a given nucleophile, reactions are classified by the substrate and leaving group, with alkyl substrates usually considered before acyl ones. Nucleophilic substitutions at a sulfur atom are treated at the end. 

Treatment with sodium hypochlorite or hypobromite converts primary amines into N-halo- or N,N-dihaloamines. Secondary amines can be converted to N-halo secondary amines. Similar reactions can be carried out on unsubstituted and N-substituted amides and on sulfonamides. With unsubstituted amides the N-halo-gen product is seldom isolated but usually rearranges (see 18-13) however, N-halo-N-alkyl amides and N-halo imides are quite stable. The important reagent NBS is made in this manner. N-Halogenation has also been accomplished with other reagents, (e.g., sodium bromite NaBr02) benzyltrimethylammonium tribromide (PhCH2NMe3 Br3"), and NCS. The mechanisms of these reactions involve attack by a positive halogen and are probably similar to those of 12-47 and 12-49.N-Fluorination can be accomplished by direct treatment of amines °° or... 

Rosokha SV, Kochi JK (2007) X-ray Structures and Electronic Spectra of the n-Halogen Complexes between Halogen Donors and Acceptors with Jt-Receptors (in this volume). Springer, Heidelberg... 

Donor/Acceptor (Structural) Effects on n-Halogen Interactions 3.4.1... 

Roewer G, Herzog U, Trommer K, Muller E, Friihauf S (2002) Silicon Carbide - A Survey of Synthetic Approaches, Properties and Applications 101 59-136 Rosa A, Ricciardi G, Gritsenko O, Baerends EJ (2004) Excitation Energies of Metal Complexes with Time-dependent Density Functional Theory 112 49-116 Rosokha SV, Kochi JK (2007) X-ray Structures and Electronic Spectra of the n-Halogen Complexes between Halogen Donors and Acceptors with jc-Receptors. 126 137-160 Rudolf P, see Golden MS (2004) 109 201-229... 

Decomposition is explosive at 155°C, and accelerated by contact with metals. See other azo compounds, n-halogen compounds... 

See other endothermic compounds, n-halogen compounds, oxidants... 

C,N-Pcrlluoro-A -aminomethyltriaminomethane, 0649 Pcrlluoro-A -cyanodiaminomethane, 0637 f Tetrafluorohydrazine, 4345 Tctrail uorourca, 0352 Tris(difluoroamino)lluoromethane, 0364 See BIS(DIFLUOROAMINO)ALKYL NITRATES See other N-HALOGEN COMPOUNDS... 

Tris(thionitrosyl)thallium, 4764 See also N -HALOGEN COMPOUNDS... 

---