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Facile synthesis of 3,4-dihydro-4,4-dimethyl-2H-pyran-2-one via palladium catalyzed terminal oxidation of 3,3-dimethyl-4-pentenoates

✍ Scribed by Mariko Tanaka; Hisao Urata; Takamasa Fuchikami

Publisher: Elsevier Science
Year: 1986
Tongue: French
Weight: 244 KB
Volume: 27
Category: Article
ISSN: 0040-4039
DOI: 10.1016/s0040-4039(00)84744-9

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✦ Synopsis

Selective terminal oxidation of 3,3-dimethyl-4-pentenoates does occur under chloride-free Wacker conditions [Pd(OAc)2/02] in AcOH to give 5-acetoxy-3.3-dimethyl-4pentenoates ( 7) and their analogues (2. 8) in good yields. Successive cyclization of 7 and 8 at vapor phase pyrolysis on SiO2 affords '3,.

Among numerous routes') for synthetic pyrethroid insecticides such as 3-(2,2dichloroethenyl)-2,2-dimethylcyclopropanecarboxylates (3), 3,4-dihydro-4,4-dimethyl_2H_pyran-2-one (1) has been thought to be one of the most hopeful key compounds for the stereoselective synthesis of more active cis-isomers. However, lack of a facile path to dihydropyranone 1 has impeded this route. The existing way to 1 from 3,3-dimethyl-4-pentenoates (4) consists of a thorny one; i.e., photochemical addition of thiophenol in the presence of BPO, chlorination by N-chlorosuccinimide, and oxidation using excess of copper(I1) salts to give 3,3-dimethyl-5oxopentanoates (2), followed by cyclization by phosphorus pentoxide. la)

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