Diastereospecific synthesis of fungicidal threo- and erythro- α-hydroxy aminals

✍ Scribed by Johann Gasteiger; Karlheinz Kaufmann

• Publisher: Elsevier Science
• Year: 1985
• Tongue: French
• Weight: 202 KB
• Volume: 26
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)98729-x

✦ Synopsis

SequentiuZ reactions of 2-chZoro-or 2-bromo-3-tert-butyloxirane with p-chloropheno-2ate nnd tken uitk sodiwn triasolate Zead in two stereocontro2led ste.ps to tkreo-Triadimenol; by inverse addition of the tuo nucleophiles the erythro-isomer is obtained. l-(4-Chlorophenoxy)-3,3-dimethyl-1-(l,Z,4-triazol-4-yl)butanol-Z (TriadimenolR, BaytanR)l, l,is an important systemic fungicide. The tkreo-isomer & is about ten times more active than the erytkro-isomer 0. 293 Thus, a synthetic approach to the pure diastereomers, particularly to &,is of much interest as it would allow a reduction in the amount of fungicide that has 1 1 to be applied. However, the presently reported processesl" lead to mixtures of mers _ and 0 which have to be separated,to provide the pure isomers. the diastereo-Cl la Ib -threo erythro The oxidation states of the carbon atoms 1 and 2 in 1 show that they can be considered as derivatives of a-hydroxy aldehydes. In previous work we have demonstrated that 2-halooxiranes' are useful intermediates for the synthesis of a-substituted carbonyl compounds. 6-9 This idea can be taken one step further on the basis of the findings reported in the preceding communi-cati0n.l' In compounds2 with a tert-butyl group in position 3 of a 2-halooxirane,the attack Buchenauer, H.; Grossmann, F., Z. Pflanzen Krankh. 89, 309 (1982).