Complex metal hydride reactivity

A combined reductive amination sequence has been developed as a useful way of synthesizing amines, with sodium cyanoborohydride as the reducing agent of choice. This complex metal hydride is a less reactive version of sodium... 

The main methods of reducing ketones to alcohols are (a) use of complex metal hydrides (b) use of alkali metals in alcohols or liquid ammonia or amines 221 (c) catalytic hydrogenation 14,217 (d) Meerwein-Ponndorf reduction.169,249 The reduction of organic compounds by complex metal hydrides, first reported in 1947,174 is a widely used technique. This chapter reviews first the main metal hydride reagents, their reactivities towards various functional groups and the conditions under which they are used to reduce ketones. The reduction of ketones by hydrides is then discussed under the headings of mechanism and stereochemistry, reduction of unsaturated ketones, and stereochemistry and selectivity of reduction of steroidal ketones. Finally reductions with the mixed hydride reagent of lithium aluminum hydride and aluminum chloride, with diborane and with iridium complexes, are briefly described. 

MH4- Complex metal hydrides LiAlH4 LiAlH(OR)3 NaBH4 NaBHjCN The more ionic MH bond is more reactive Substitutions Additions. Deprotonates acidic Hs on heteroatoms NaH and KHas MH bases... 

The literature on this area up to 1990 has been reviewed in a major volume. The ability of complex metal hydride acceptors to stabilise p,-bonded phosphorus compounds, but without diminishing their reactivity, has also been reviewed. ... 

Nitrogen heterooycles, reduction of, with complex metal hydrides, 6, 45 Nitrogen heterocyclic systems, Claisen rearrangements in, 8, 143 Nucleophiles, reactivity of azine derivatives with, 4, 145... 

The complex metal hydrides can effect replacement of halogen or sulfonate groups under reaction conditions that favor Sn2 processes. Sodium borohydride in solvents such as DMSO or sulfolane that enhance nucleophilic reactivity has been... 

The reaction of the coordinatively unsaturated ruthenium amidinates with [Cp RuCl]4 tetramer or [CpRufMeCNlsJPFg provides access to novel amidinate-bridged dinuclear ruthenium complexes (Scheme 146), which in turn can be transformed into cationic complexes or hydride derivatives. In these complexes, a bridging amidinate ligand perpendicular to the metal-metal axis effectively stabilizes the highly reactive cationic diruthenium species. 

The fact that both the thermal and the photochemical insertion reactions yield the same products via formation of charge-transfer complexes leads to the conclusion that the reactive ion-radical pair in equation (52) is the common intermediate for both activation processes. Such a conclusion is further verified by the direct observation of anion-radical intermediates from the thermal reaction of TCNE and DDQ with various metal hydrides.188... 

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