Grignard bifunctional

The use of the y-(trimethylsiloxy)nitrile derivatives (190) as a route to 1,4-bifunctional units is exemplified in a convenient synthesis of jasmonoid compounds. The addition of the Grignard reagent to the cyano group as the homologation step results in the keto alcohol (191) after subsequent hydration. The y-ketocarboxylic add (192) obtained from the... 

Similarly, organolithiums (or Grignard reagents) add to ester (26) to afford silyl enolates which are intercepted with aldehydes and ketones to give a,p-unsaturated esters (27),434 while addition of the bifunctional aryllithium (28) (MIRC protocol) affords the 2-(trimethylsilyl)tetrahydronaphthoate ester (29 Scheme 7).43b... 

Bicyciic methy/enecyclopentanes. Trostand Chan2 have extended their synthesis of mcthylenecyclopentanes by cycloaddition of trimethylenemethanepalladium complexes to alkenes (9,454-455J3 to an intramolecular [3 + 2] cycloaddition to give bicyciic mcthylenecyclopentanes. The substrates (2) can be prepared by reaction of Ihc Grignard reagent prepared from 2-bromo-3-(trimethylsilyl)propene (1) with a suitable bifunctional aldehyde (equation I). 

Z)-Disubstituted alkenes. The (Z)-vinylstannane 2 is readily prepared by hy-droalumination of propargyl alcohol followed by stannylation with tri-n-butyltin triflate. Another route to (Z)-vinylstannanes is shown in equation (11). The bifunctional 2 is useful for iterative coupling to (Z)-polyolefins. Thus 3 is converted into the vinyl Grignard... 

Bifunctional dithiophosphinic acids, HS(S)RPZPR(S)SH, R = Me, Ph, j9-anisyl Z=1,4-C6H4, (CH2) with n = 4-10, and some of their salts and complexes, have been prepared from cyclic [RP(S)S]2 with di-Grignard reagents, BrMgZMgBr.28,29... 

In the following case a carbonate could not be removed in the presence of the diolide using hydrolytic conditions. It was found that treatment with the bifunctional Grignard reagent cleaved the carbonate in 65% yield by taking advantage of the intramolecularity of the second addition. ... 

A possible method seemed to be to make use of the Thorpe-Ingold, or gem-dimethyl, effect which, in one statement 49), is that the accumulation of substituents along the chain of a bifunctional system appears to selectively stabilize the corresponding cyclic forms. Maercker and co-workers (6S) have recently used this effect to shift the equilibrium between a 3-butenyl Grignard reagent and a cyclopropyl methyl Grignard reagent in favor of the cyclopropylmethyl compound. 

Nickel-catalysed cross-coupling of aryl bromides with tertiary Grignard reagents has been performed in the presence of donor-functionalized A-heterocyclic carbenes. Bifunctional A-heterocyclic carbene ligands (e.g. 15) were shown to result in especially selective and efficient transformations. 

Bifunctional Halides 1971. Investigating the preparation of 1,1-bifunctional Grignard reagents use was made of a Barbier-type of reaction in which a 1,1-dihalide reacted with magnesium in the presence of an aldehyde or a ketone [98] (diethyl ether or an ether/benzene mixture was used as the solvent) ... 

Finally, the polycondensation reaction between bifunctional Grignard reagents and aryldimethoxyboranes, carried out under a nitrogen atmosphere, in THF, gives rise to poly(phenylene-boranes) (20) (eq. 20) (83). The conjugated polymers may have potential apphcations in electronic devices such as LEDs. 

Almost quantitative carboxyl formation is observed if the polymer is converted to an intermediate Grignard (171) compound. The CO2 is added rapidly, accompanied by a significant increase in viscosity of the monofunctional polymers and gelling of the bifunctional polymers. Yields depend on the reaction rates and on stirring efficiency. Alternatively, a anhydride can be used as termination agent (reaction 41). 

Bifunctional Grignard reagents may also be used for the synthesis of boron heterocyclics (36-39). Reaction of (m-C4H9)2BC1 with the di-Grignard of Br(CH2) Br (n = 4, 5) gives B-n-butylboracyclanes. 

In the same vein, cyclic phosphines such as 1-phenylphosphocyclohexane can be prepared by the reaction of the corresponding bifunctional Grignard reagent, generated from, for example, 1,5-dibromopentane, with the corresponding dichloro-phenylphosphine (Scheme 10.49). 

Scheme 10.49. A bifunctional Grignard reagent imdergoing reaction with a dihalophosphine to produce a heterocycle phosphine (1-phenylphosphocyclohexane).

An up-to-date account of the chemistry of the alkanes has been published. The neopentyl substituent has been reviewed. A general method for the synthesis of hydrocarbons interspersed with ew-dimethyl units has been described the key reaction is the conjugate addition of bifunctional Grignard reagents to diethyl isopropylidenemalonate (Scheme 1). Aluminium alkyls... 

The action of Grignard reagents on N-(5-aryl-3H-l,2-dithiol-3-ylidene)-arylamines (10) provides the 1,3-bifunctional reagents (11)," which have proved to be versatile starting materials in heterocyclic syntheses. Their oxidation with iodine produces isothiazolium iodides (12) in 29—34% yield. 

---