preparation of thermodynamic silyl enol ethers

Tetrahedron Letters,Vol.24,No.l3,pp 1345-1348,1983

There now exist a variety of mild and very selective procedures for the kinetic
deprotonation of unsymmetrical ketones employing alkali metal dialkylamides. The "kinetic"
enolates produced in this way may be efficiently trapped by trimethylsilyl chloride to
regiospecifically provide the less substituted trimethylsilyl enol ethers.1 Despite the
recent introduction of several new methods, there are still no procedures available which
allow direct3 regiospecific preparation of the more substituted "thermodynamic" enolates or
trimethylsilyl enol ethers.

 

this paper described a way using MeMgBr/diisopropylamine to generate the thermodynamic enolate at rt, which worked out as described.(HMPA is necessary, without it, no rxn at all).

a mild alternative nitrene generation method for C-H amination

current method involve hypervalence iodine to oxidize the carbamate or sulfonamates to the imidoiodo species followed by metal incorperation to do following C-H aminations.
One problem limiting the rxn scope and catalyst preformance is the the high-oxidative potencial of the hypervalenc iodine compund such as pida, pifa.

here I propose a new oxidant which is a imidoiodo compound with a bulky blocking group attached to the imine. It is a milder oxidant than the pida/pifa and with a certain sized bulky group, the oxidant might be able to exchange its iodo with  a carbamte but not able to react with the metal like rhodium.
Such a setup can increase the catalyst scope and performance and also milder the rxn condition.