REDUCTION OF ALKYL HALIDES AND

The tin hydrides find important applications as reducing agents. Many of their reactions (particularly the reduction of alkyl halides and the hydrostannation of simple alkenes and alkynes) arc known to proceed through RaSn- intermediates, and this aspect of their chemistry is referred to in Section II,G. 

Trialkyltin radicals are important intermediates in the reduction of alkyl halides, and in the hydrostannation of alkenes (1, 287). 

REDUCTION OF ALKYL HALIDES AND TOSYLATES WITH SODIUM CYANOBOROHYDRIDE IN HEXAMETHYL-PHOSPHORAMIDE (HMPA) A. 1-IODODECANE TO n—DECANE B. 1-DODECYL TOSYLATE TO n-DODECANE, 53, 107 REDUCTION OF KETONES BY USE OF TOSYLHYDRAZONE DERIVATIVES ANDROSTAN-17 0—OL, 52, 122 REDUCTIVE AMINATION WITH SO-... 

It is known that the [Ni(I)(OEiBC)] complex mediates electrocatalytic reductions of alkyl halides and methyl p-toluenesulfonate [305]. The nucleophilic-ity of the Ni(I) complex is comparable to that of the supernucleophile vitamin Bi2. Recently, the formation of... 

Alkylnickel formation has also been extensively studied in the one-electron reductions of alkyl halides and peroxides by a nickel(I) macrocycle (189, 196, 197). Although two forms of the nickel(II) isomers of the tetra-N-methylated macrocycle are known, there is no ready interconversion between the [(f ,f ,S,S,)Nin(tmc)]2+ and [(i ,S,S,/ )]Ni"(tmc)]2+. Solutions of the [Ni (tmc)]+ complexes can be prepared in alkaline media (183), although within several Hours isomerization of the nickel(I) forms takes place. The complexes are again strong reductants (E° = — 0.90 V). Using the lft,4ft,8S,llS isomer (Fig. 12), Espenson and his co-workers have examined reactions with a variety of primary alkyl halides (189). For most systems studied, the overall reactions exhibit the stoichiometry according to Eq. (20) ... 

REDUCTION OF ALKYL HALIDES AND TOSYLATES WITH SODIUM CYANOBOROHYDRIDE IN HEXAMETHYLPHOS-PHORAMEDE (HMPA) ... 

These preparations that illustrate the use of sodium cyanoborohydride in hexamethylphosphoramide as an effective, selective, and convenient procedure for the reduction of alkyl halides and tosylates is essentially the same as previously described.8 The very mild reducing ability of sodium cyanoborohydride makes the method particularly valuable when other functional groups are present in the molecule... 

Besides new insight into the reactivity of free radicals, methods for die production of carbon-centered free radicals have also seen major improvements in die last several years. One very common new mediod is to use tin-based reagents as radical chain carriers. Trialkyltin radicals readily abstract bromine or iodine from carbon to produce a carbon-centered free radical. Placement of a bromide or iodide substituent on a substrate dius permits formation of a carbon-centered free radical at diat position using tin-based mediodology. This process was initially developed for die reduction of alkyl halides, and it remains an excellent synthetic method for diat purpose. The complete chain mechanism for die reduction is shown. 

Reduction of alkyl halides and sulfonate estersThis reagent in HMPT is Nomcwhat more effective than NaBH3CN for reduction of primary alkyl iodides and allylic and benzylic iodides. It is also preferred for reduction in benzene or CH2C12. 

The polyHIPE supported thiol is a good catalyst for radical reduction of alkyl halides and reductive cyclisations of e-bromoalkenes by triethylsilane. 

Reduction of alkyl halides and tosylates. - Reduction with sodium cyanoborohydride in HMPT provides a rapid and selective removal of iodo. bromo, and tosyloxy groups in high yield. Thus 1-iododecane can be reduced in thi.s way to n-deeane in... 

The reaction of thiyl radicals with silicon hydrides [Reaction 1] is the key step of the so-called polarity reversal catalysis that has been utilised extensively in the radical chain reductions of alkyl halides and also in the hydrosilylation of... 

Reactions.—The use of NaBH, in polar aprotic solvents as a convenient and effective source of nucleophilic hydrogen for the reduction of alkyl halides (and tosylates) to alkanes has been reported in full this year. This reagent is selective and does not affect other functional groups such as ester or nitrile (contrast LiAlH4). Sodium trimethoxyborohydride is an alternative, especially for reduction in the presence of alkene functions this report also includes details of a one-pot sequence from alcohols via the iodides to alkanes (Scheme 46). ... 

To date there are no reported examples of the above molecules catalyzing a reaction, however Lacote, Curran et al. recently demonstrated that their NHC-stabilized boryl radicals (85, vide supra) can serve as radical initiators for acrylate polymerizations, radical deoxygenation reagents, radical reductions of alkyl halides and radical chain homolytic substitution reactions. ... 

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