Group 13 amides thallium

The dimeric thallium(III) amide [( fo (pentafluorophenyl) Tl(dpa))]2 " (where Hdpa = 2,2 -dipyridylamine) comprises distorted trigonal bipyramidal thallium(III) ions that are coordinated by two pentafluorophenyl groups (TI—C distances are 2.12(4) and 2.16... 

The chemistry of alkyl- and arylaluminum, gallium, indium, and thallium amides has been investigated much more than the comparable chemistry of Group II elements (9,13-18). Alkylaluminum amides especially have a very rich and diverse structural chemistry (9,13-15). When a trialkylalane reacts with primary or secondary amines, the amides 3,3, and 4 are formed in addition to a simple adduct [Eqs. (3) and (4)]. 

Salts of mercury(II) and thallium(HI), such as mercury(II) acetate, Hg(OAc)2, and thallium trifluoroacetate, Tl(OCOCF3)3, are reactive electrophilic metallating species which attack benzene directly. Electron-donating groups in the aromatic ring accelerate the reaction in the conventional manner and direct attack to the ortho and para positions. In addition, metal-chelating substituents, such as amide, promote the reaction and direct attack to the 2-position in a manner similar to that seen in the directed orthometallation reaction. 

It is important to note that cleavage of the 5-(acetamidomethyl) group with metal ions, such as thallium(III) trifluoroacetate, or with iodine may lead to alkylation of hydroxy groups,as well as of amide groups,P l via reactive acetamidomethanol intermediates. These side reactions are minimized by the use of glycerol as a scavenger. 

Alkenes and alcohols condense with nitriles under drastic acidic conditions. In most cases sulfuric acid is used either neat or with solvents such as acetic acid. In liquid hydrogen fluoride containing defined amounts of water, nitriles react with linear or branched alkenes to form amides in good yields. Treatment of allylsilanes and allylstannanes with thallium(III) salts in acetonitrile activates Ae alkene for nucleophilic attack of the nitrile group. The generated nitrilium cation (equation 23) is hydrolyzed to the corresponding )V-allylamide. ... 

In this case, the modified Heck reaction of amide 220 bearing fully protected functional groups, which was prepared from 5S,6S-bis(methoxy-methoxy)-4-(4f )-azidocyclohex-2-enone, is a key step. The protected amide 220 underwent intramolecular cyclization with palladium acetate in the presence of thallium(I) acetate and l,2-bis(diphenylphosphono)ethane... 

A further displacement of practical utility is that of halogen in phosphonic and phos-phinic chlorides by carboxylate ions (with silver or thallium salts, for example) to give mixed anhydrides, e.g. 581 and 582. Such anhydride formation provides a system particularly reactive at the carbonyl group towards nucleophiles, and thus preliminary activation of the carboxyl group by the diphenylphosphinoyl group becomes useful in amide or peptide formation ... 

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