Reductive transpositions

ClP0(0-i-Pr)2l py/ NaFe(CO)2Cp/HBF4/NaI p-TsNHNH2 / NaOAc, HOAc 

NaBHjCN, n-BuZnCl or LiHB(xec-Bu)3 cat Pd(PPh3)4 cat phosphine 

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We again treat the case of reductions. Transposition to oxidations is straightforward using the same changes of sign as defined in Section 1.2. For attached (or immobilized) reactants, the surface concentrations of the three reactants obey two of Nemst s laws ... 

P-Siloxy-e-acetoxy--y,8-unsaturated carbonyl compounds undergo reductive transposition on exposure to HCOONH4, (dba)3Pd2, and BuiP in DMF to afford the 8,e-unsaturated products with (all) syn-isomers predominating.- In conjunction with the enantioselective aldol access to the substrates, this process expands the methodology of existing polyketide synthesis. 

Hair transplantation Scalp reduction Transposition flap Soft tissue expansion... 

The mild reaction conditions for the displacement and hydrolysis steps combined with the spontaneous sigmatropic loss of dinitrogen allow the use of this chemistry in complex settings, including conjugated systems, to afford the desired reduction products (eq 4). This chemistry provides the desired reductive transposition products even in recalcitrant substrates for the invertive Mitsunobu displacement reaction (eq 5). 

Reductive Transposition of Allylic Alcohols. Similar to the synthesis of allenes from propargylic alcohols, the Mitsunobu displacement of allylic alcohols with IPNBSH followed by hydrolysis, diazene formation, and sigmatropic loss of dinitrogen provides reductively transposed alkenes. This methodology has proven effective for the reductive transposition of a variety of allylic alcohols (eq 2). The overall transformation provides the desired olefin with high selectivity in the formation of the irans-alkene (eq 3). ... 

Reductive Transposition of Allylic Halides. Displacement of allylic leaving groups with the sodium sulfonamide of IPNBSH followed by in situ hydrolysis, allylic monoalkyl diazene formation, and sigmatropic loss of dinitrogen affords the reductively transposed product (eq 6). 

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