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Formal total synthesis of (-)-balanol: concise approach to the hexahydroazepine segment based on RCM.

The Journal of organic chemistry (2000-04-06)
A Fürstner, O R Thiel
ABSTRACT

A concise synthesis of the hexahydroazepine moiety 13 of (-)-balanol 1 is described that comprises only eight steps and is distinctly shorter than all previous reported approaches to this particular compound. Sharpless epoxidation of divinylcarbinol 4 and ring closing alkene metathesis (RCM) reaction for the formation of the heterocyclic scaffold 9 constitute the key transformations of this sequence. The latter reaction is best achieved with catalytic amounts of the ruthenium indenylidene complex 18 recently reported. Furthermore, it is demonstrated that RCM can be successfully carried out even in the presence of an azido function provided that Schrock's molybdenum alkylidene complex Mo(=NAr)(=CHCMe2Ph)[OC(Me)(CF3)2]2 (Ar = 2,6-diisopropylphenyl) is used as precatalyst.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Hexamethyleneimine, 99%
Sigma-Aldrich
Diethyl azodicarboxylate solution, 40 wt. % in toluene