Type 2 Intramolecular <i>N</i>-Acylazo Diels−Alder Reaction: Regio- and Stereoselective Synthesis of Bridgehead Bicyclic 1,2-Diazines
作者:Claudia L. Molina、Chun P. Chow、Kenneth J. Shea
DOI:10.1021/jo070978f
日期:2007.8.31
The type 2 intramolecular N-acylazo Diels−Alder reaction provides a regio- and stereoselective synthesis of bicyclic 1,2-diazine systems. A new method for the generation of N-acylazo dienophiles with tetra-n-butylammonium periodate is reported. X-ray crystallographic analysis allowed the quantification of structural distortions of the nonplanar bridgehead olefin and lactam functionalities in 1,2-diazine
of electrophilic azo reagents with NHC-boranes leads to the formation of NHC complexes of mono- and bis-hydrazino boranes with N−N−B and N−N−B−N−N chains. Steric hindrance on the carbene (primarily) and on the azo reagent (somewhat less) is crucial for the reactivity. Bis-hydrazino borane complexes with two different hydrazine arms could be obtained via sequential additions.
The invention provides azocarbonyl-functionalized silanes of the general formula I (R1)3-a(R2)aSi-RI-NH-C(O)-N=N-R4.
They are prepared by a procedure in which in a first step hydrazine of the formula H2N-NH-R4 reacts
with an isocyanatosilane of the general formula (R1)3-a(R2)aSi-RI-NCO,
and in a second step the product of the first step is oxidized with an oxidant, or
in which in a first step hydrazine of the formula H2N-NH-R4 reacts
with an acyl halide of the general formula Cl-C(O)-O-R5,
in a second step the product of the first step is oxidized with an oxidant and
in a third step the product of the second step reacts with an aminosilane of the general formula (R1)3-a(R2)aSi-RI-NH2.
It may be used for moldings.