ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Rearrangement of α-Halogen- to α′-Halogen-cyclobutanones, Key Step of a Highly Versatile Synthesis of Pyrethroidsα-Halogenocyclobutanones, which are readily available by [2 + 2]-cycloaddition of haloketenes to terminal olefins (e. g. 5 → 6), undergo an efficient and stereoselective cine-rearrangement to α′-halogenocyclobutanones in the presence of catalysts such as tertiary amines, HX acids or quaternary ammonium salts (e. g. 6 → 7, Table 1). Preparative as well as mechanistic aspects of the cine-rearrangement are discussed. The 2,4-cis-disubstituted cyclobutanones 7-32 thus formed represent valuable intermediates in a new synthesis of pyrethroids 1.The X-ray structure of 2-chloro-4-(2,2,2-trichloroethyl)-3,3-dimethylcyclobutanone (7), the most important precursor of cis-3 (X = Cl) shows the following features: a puckered cyclobutanone ring (dihedral angle 31°), 2,4-cis-di-pseudoequatorial arrangement of the chloro and trichloroethyl substituents, and an endo-deviation (0.225 Å; 11°) of the carbonyl O-atom from the plane formed by C(1), C(2) and C(4) (Fig. 2).
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19810640813
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