- Mechanism and stereoselectivity of the aza-Wittig reaction between phosphazenes and aldehydes
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The mechanism of the aza-Wittig reaction between phosphazenes and aldehydes has been studied computationally, using DFT methods (B3LYP/6-31G* level), and experimentally. It has been found that the reaction consists of a tandem [2+2] cycloaddition-cycloreversion sequence in which π and σ orbitals as well as lone pairs are involved. Both [2+2] processes take place via thermally allowed supra-supra mechanisms. P-trimethyl-λ5- phosphazenes are predicted to be more reactive than their P-triphenyl analogues. The stereochemical outcome of the whole reaction depends only on the second step, because conformational changes in the intermediate 1,3,2- λ5-oxazaphosphazetidines have a much lower activation energy than the second [2+2] cycloreversion reaction. Preferential or exclusive formation of the corresponding (E)-imines is predicted.
- Cossio, Fernando P.,Alonso, Concepcion,Lecea, Begona,Ayerbe, Mirari,Rubiales, Gloria,Palacios, Francisco
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p. 2839 - 2847
(2007/10/03)
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- One-pot conversion of azides to Boc-protected amines with trimethylphosphine and Boc-ON
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Reaction of azides with trimethylphosphine followed by addition of 2- (tert-butoxycarbonyloxyimino)-2-phenyl-acetonitrile (Boc-ON) at -20°C and stirring at r.t. for 5 h affords the desired Boc-amines in 87-100% yields. Similar types are obtained by mixing
- Ariza, Xavier,Urpi, Felix,Viladomat, Carles,Vilarrasa, Jaume
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p. 9101 - 9102
(2007/10/03)
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