Coupling of allylic halides promoted by iron metal dispersed in dimethyl formamide

Abstract

The coupling reaction of allylic halides to produce non-conjugated dienes was investigated. It was found that iron powder could be utilized, without any special pretreatment, to promote the coupling reaction when a dipolar aprotic solvent was employed as the rcaction medium.Effects of variables such as thc nature of the halogen atom in the reactive position of the substrate, substituents on the substrate, Dresence or absence of organic or inorganic halide catalysts, and solvent type were explored briefly.Non-conjugated dienes can be prepared in yields which exceed 90% in the Inore favorable cases. The present procedure avoids many of the difficulties inherent in such previous rnetl~ods as the Grignard reaction or the nickel carbonyl-promoted reaction.

Selective .gamma. alkylation of dienolate anions derived from .alpha.,.beta.-unsaturated acids. Applications to the synthesis of isoprenoid olefins

“…The products were isolated on preparative GLC (column D) and both shown to be -alkylation products: A was 9, derived from Sn2' attack, and B was 8a, from Sn2 attack. Peak A, methyl (£)-2,5,6-trimethyl-2,6-heptadienoate (9) (substitution with transposition): NMR (CC14) 6.59 (br t, 1), 4.66 (d, J = 0.5 Hz, 2), 3.63 (s, 3), 2.2 (m, 3), 1.77 (d, J = 0.3 Hz, 3), 1.67 (d, J = 0.5 Hz, 3), and 1.3 (d, J = 6 Hz, 3).…”

Methods Utilizing First-Row Transition Metals in Natural Product Total Synthesis

“…One powerful methodology along these lines is the reductive coupling of alkyl, allylic, and benzylic halides. Beginning in the 1940s, first-row transition metals including nickel tetracarbonyl were first used to form C sp3 –C sp3 bonds by the homocoupling of allylic halides. , The general propensity of first-row transition metals to engage in single electron chemistry has led to the discovery of variants of this reaction using not only Ni, but Ti, − V, Cr, Fe, − Mn, Co, − and Cu. , …”