| Abstrakt: |
Reactions of 5,5,5-trichloro-3-penten-2-one (1) with a number of nucleophiles have been carried out. It was found that the Grignard reagents (5) primarily attacked the carbonyl carbon of 1yielding the corresponding tertiary alcohols (7). The reaction sequence of ethylmagnesium bromide (5a) is given as an example. The reaction of 5awith 1gave 6,6,6-trichloro-3-methyl-4-hexen-3-ol (7a) as the major constituent of the primary product. The hexenol 7areadily underwent the allylic rearrangement by heating at distilling temperature (88–90°C/6 mmHg) to afford 4,6,6-trichloro-3-methyl-5-hexen-3-ol (8a), which was in turn converted into 6,6-dichloro-3-methyl-3,4-epoxy-5-hexene (9a) by treatment with sodium methoxide. The stereoselective synthesis of dl-erythro-4,6,6-trichloro-3-methyl-5-hexen-3-ol (8a-I) was achieved by using 3,5,5-trichloro-4-penten-2-one (3) as the starting material in place of 1. dl-trans-6,6-Dichloro-3-methyl-3,4-epoxy-5-hexene (9a-I) was derived by the cyclization of 8a-Iwith a base. The stereochemistry of 8aand 9awas discussed on the basis of NMR data. Nucleophiles such as methanol, hydrogen chloride, anilines, thiophenol, sodium acetate, sodium phenolate, and diethyl sodiomalonate gave the products of the conjugate addition (15). Ethyl sodioacetoacetate gave 2-chloro-3-acetonyl-4-ethoxycarbonyl-5-methylfuran (17). |
