B. Tao, J. W. Timberlake
Dec 19, 2000
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ChemInform
Abstract
Conformationally constrained dibenzo[a,d]cycloheptadiene-based spirohydantoins were prepared from dibenzosuberone via the transformation of the a-hydroxy ester to the azido ester, followed by its reduction to the amino ester, and cyclization of the carbomethoxy N,N’-asymmetric ureas, derived from the amino ester with triphosgene and a variety of amines. A novel ring expansion reaction was also observed in the process.