Synlett 2007(19): 2927-2936  
DOI: 10.1055/s-2007-992370
ACCOUNT
© Georg Thieme Verlag Stuttgart · New York

Evolution, Development and Personal Experience in Studies of the Allyl Cyanate-to-Isocyanate Rearrangement

Yoshiyasu Ichikawa*
Faculty of Science, Kochi University, Akebono-cho, Kochi 780-8520, Japan
Fax: +81(88)8448359; e-Mail: ichikawa@kochi-u.ac.jp;
Weitere Informationen

Publikationsverlauf

Received 23 March 2007
Publikationsdatum:
12. November 2007 (online)

Abstract

Evolution and development of the synthesis and rearrangement of allyl cyanate is described. Allyl cyanate-to-isocyanate rearrangement is a concerted [3.3]-sigmatropic process involving highly selective [1,3]-chirality transfer to the newly formed asymmetric center bearing nitrogen. The usefulness of this rearrangement is manifested by the synthesis of natural products containing nitrogen-substituted quaternary carbon atoms.

1 Background

2 Evolution of the Allyl Cyanate-to-Isocyanate Rearrangement. A Personal History

3 The Stereochemistry and Mechanism of the Allyl Cyanate-to-Isocyanate Rearrangement

4 Synthesis of Natural Products Containing Nitrogen-Substituted Quaternary Carbon Centers

5 Coda

18

To a solution of commercially available nerolidol 41 (a 3:2 mixture of Z- and E-isomers 5.01 g) in hexane cooled to 0 °C was added acetonitrile (14 ml) and TFA (8.0 ml). The resulting biphasic mixture was vigorously stirred at 0 °C for 24 h and then poured into aq NaHCO3. Usual workup followed by silica gel chromatography (hexane → diethyl ether-hexane, 1:2) gave the recovered starting material (1.23 g) and crude products which were purified by recrystalli-zation (ether and hexane) to furnish aminobisabolenes (a 2:1 mixture of 37 and 38, 195 mg, 4.4% yield based upon the consumed starting materials).