Allylmagnesium reagents

Yamamoto et al. have reported selective y-coupling of an allylmagnesium reagent wifh diphenylphosphates [36]. Reaction of ( )-2-decenyl 1-diphenylphosphate with 1.1 equiv. 2-cyclopentylideneethylmagnesium chloride in THF at -20°C gave the y-alkylated product in 86% yield wifh a y/a ratio of 99 1 (Eq. 1). Thus, the y-carbon of fhe Grignard reagent attacked fhe primary carbon of the phosphate (Scheme 3.61). 

Ordinary hydromagncsialion may be effected by the use of a nickel-pyridine complex like Ni(py)4Ch. even though it affords a mixture of rcgioisomcrie allylmagnesium reagents as determined by carboxylalion. giving two kinds of carboxylic acids (eq. 3.37) (5(). An alkoxybntadicne underwent the alkylation as well... 

The sonochemical addition proceeds rapidly in excellent yield. 0 Sonication accelerates the addition of allylmagnesium reagents to oximes with a trifluoro-... 

Quinoxalines undergo facile addition reactions with nucleophilic reagents. The reaction of quinoxaline with allylmagnesium bromide gives, after hydrolysis of the initial adduct, 86% of 2,3-diallyl-l,2,3,4-tetrahydroquinoxaline. Quinoxaline is more reactive to this nucleophile than related aza-heterocyclic compounds, and the observed order of reactivity is pyridine < quinoline isoquinoline < phenan-thridine acridine < quinoxaline. ... 

In general, there are three main types of allyltitanium reagent, usually prepared in situ from allyllithium or allylmagnesium derivatives ... 

Both reagents 7 and 9 are also excellently suited for the introduction of 3-substituted allyl residues. Both high simple anti) diastereoselectivity and enantioselectivity are observed, irrespective of the configuration of the double bond in the allylmagnesium, -potassium, or -lithium reagent used for the in situ preparation 11,35 36. 

Structural rearrangements are not encountered with saturated Grignard reagents, but allylic and homoallylic systems can give products resulting from isomerization. NMR studies indicate that allylmagnesium bromide exists as a CT-bonded structure in which there is rapid equilibration of the two terminal carbons.101 Similarly,... 

Preparation. The reagent can be prepared in 94% yield by the reaction of allylmagnesium bromide with bis(tributyltin) oxide in ether. Sonication is useful for initiation of the Grignard reaction. 

In 1974, Vermeer et al. described formation of allenic alcohols 61 by the reaction of alkynyl epoxides 60 with Grignard reagents in the presence of 10mol% of Cul (Scheme 3.33) [71]. In the absence of Cul, a complicated mixture of products was obtained. Furthermore, the Cu-catalyzed reactions exhibited higher yields and higher selectivity than analogous reactions of alkynyl epoxides with lithium dialkylcup-rates [72], This method was applied to a reaction of allylmagnesium bromide with an alkynyl epoxide [73]. 

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