A convenient synthesis of naturally occurring quinizarins

✍ Scribed by Bruno Simoneau; Paul Brassard

• Publisher: Elsevier Science
• Year: 1988
• Tongue: French
• Weight: 731 KB
• Volume: 44
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)85881-6

✦ Synopsis

I'mted 8x1 Cm11 Bnta~n.

B. SIMOSLW and P. BILASSA~D 781 yield OP the corresponding products in a 2.9: 1.0 ratio).

A combination consisting largely oP the E-isomer could also be obtained by the use oP trimethylsilyl triilate in triethylamine" but the yield did not exceed 561. Analogoua compounds have also recently been prepared by an iodotrimethylsilane -induced rearrangement oP 2-siloxycyclopropanecarboxylates*~.

A second enolization, using the Corey and Gross procedure", was carried out on the Poregoing esters 2a.b and gave slightly better yields of a purer product (85-901) than with the method used previously*. Under these two sets oP conditions, the proportions OP stereoisomers can be quite diPPerent but it has been shown in another case that the distribution of isomers has little effect on subsequent cycloadditions. Thus, ester ?a gave a mixture oP three isomers (a Pourth is barely perceptible) oP Z,Z-, E.Z-and Z,E-configuration in a 2.9: 0.9: 1.0 ratio and the method seems to