Grignard reagents lead compounds

The morpholin-4-yl substituent in 7-position behaves similarly to the ethoxy group. Compound 481 is easily prepared by double addition of benzotriazole to acrolein followed by elimination of one of the benzotriazolyl moieties induced by treatment with NaH. Lithiation of derivative 481 followed by addition to a Schiff base results in formation of diarylpyrrole 476. Lithiated product 481 is alkylated exclusively at the carbon a, in relation to the benzotriazolyl substituent, giving intermediate 482. Subsequent treatment with a Grignard reagent leads to enamine 483 (Scheme 79) <1995TL343>. 

The low temperature reaction of pentanedial with a range of alkyl Grignard reagents leads to 6-substituted tetrahydropyran-2-ols (72HCA249). The major side reaction involves addition of the organometallic compound to both carbonyl groups. 

Reaction of a phthalonitrile with a Grignard reagent leads to a phthalocyanine analogue in which one of the meso nitrogens is replaced by carbon - the so-called tetraben-zotriazaporphyrins [208, 209]. Leznoff and coworkers [210] have used this reaction to prepare a discotic liquid crystalline derivative (Scheme 54). Compound 47 forms a... 

The mechanism involves the formation of a nucleophilic ferrate species from the iron(IIl) salt and ter/-butylmagnesium chloride. It undergoes oxidative addition to the aryl halide. Transmetalation with the Grignard reagent leads to an alkyliron compound. The latter is not preferentially prone to reductive elimination to form alkylated arenes. Instead, P-hydride elimination and subsequent reductive elimination of the hydrido-iron complex reforms the iron(-II) catalyst releasing isobutene and the defiinctionalized arene (Scheme 4-226). ... 

Cyclization of the side chain onto the nitrogen atom leads to compounds with sedative and tranquilizing activity. The lack of structural specificity, that is, the fact that both positional isomers (41,43) show the same activity, is notable. Thus, condensation of the Grignard reagent from 2-bromopyridine with ben-zophenone affords the tertiary carbinol, 40. Catalytic reduction... 

A closely related reaction of (—)-(S)-276 with the Grignard reagents obtained from a-acetylenic halides leads to the formation of mixtures of acetylenic sulphoxides 290 and allenic sulphoxides 291363 (equation 161). The latter compounds are most probably formed via transition state 292, which is analogous to 289. On the other hand, hex-l-ynyl p-tolyl sulphoxide 293 is smoothly prepared from hex-1 -ynylmagnesium bromide and (— )-(S)-276363 (equation 162). 

Next to the formation of Grignard reagents, the most important application of this reaction is the conversion of alkyl and aryl halides to organolithium compounds, but it has also been carried out with many other metals, (e.g., Na, Be, Zn, Hg, As, Sb, and Sn). With sodium, the Wurtz reaction (10-93) is an important side reaction. In some cases, where the reaction between a halide and a metal is too slow, an alloy of the metal with potassium or sodium can be used instead. The most important example is the preparation of tetraethyl lead from ethyl bromide and a Pb—Na alloy. 

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