2,2-Di:methyl-3-di:halovinyl- cyclopropane-carboxylate(s) prepn. - from 2,2-di:methyl-3-butenyl ketone and tetra:halo-methane cpds.

摘要

Prepn. of trans-rich 2,2-dimethyl- 3-(2,2-dihalovinyl)- cyclopropanecarboxylic acid derivs. of formula (I) is carried out by (a) reacting an alkyl 2,2-dimethyl 3-butenyl ketone of formula R1CH=CH-C(Me)2-CHR3-COR2 (II) with a tetrahalomethane XCY1Y2Y3 to form an alkyl 2,2-dimethyl- 3,5,5,5-tetrahalopentyl ketone (IV); (b) reacting (IV) with a base under severe conditions to form a trans-rich 2,2-dimethyl- 3-(2,2-dihalovinyl) cyclopropyl ketone of formula (V); and (c) oxidising (V) to give (I). In the formulae X is Cl or Br; Y1-Y3 are F, Cl or Br, provided that Y1-Y3 are F or Cl when X is Cl; R1 is H or alkyl; R2 is alkyl; R3 is H, lower alkyl, acyl, COOH or alkoxycarbonyl; R is H or lower alkyl. (I) are useful as intermediates for pyrethroid insecticides.