Grignard reagents alkynic

Another feature of the Pd—C bonds is the excellent functional group tolerance. They are inert to many functional groups, except alkenes and alkynes and iodides and bromides attached to sp carbons, and not sensitive to H2O, ROH, and even RCO H. In this sense, they are very different from Grignard reagents, which react with carbonyl groups and are easily protonated. 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

Addition of alkynes to a-alkoxy aldehydes is most favorably performed with the corresponding zinc reagents (Table 12)46. As with Grignard reagents, the chelation-controlled addition of zinc alkynes proceeds with higher diastereoselectivity when diethyl ether rather than tetrahydrofuran is used as reaction solvent. 

The simple hexaalkylditins, RsSnSnRs, do not disproportionate on heating, but, in oxolane (tetrahydrofuran) or acetonitrile in the presence of a base such as a Grignard reagent, or in the more strongly basic solvent hexamethylphosphoric triamide (HMPT), disproportionation readily occurs at room temperature, and, in HMPT, addition occurs to such alkynes as phenylacetylene and diphenylbutadiyne. The disproportionation is considered to proceed by nucleophilic attack upon tin (259, 260), e.g.,... 

Cleavage of propargyl ethers by Grignard reagents 12-2 Rearrangement of alkynes... 

Jacobi reports using a variant of method A to access the A,B,E-ring system of wortmannin.14 The sequential addition of methyl lithium and acetylenic Grignard reagent followed by triflation proceeds from 7 to the corresponding triflate 8 in 74% yield (Fig. 4.13). Subsequent carbonylation of the alkyne and the phenol produces the acyl oxazole 9, which is smoothly converted into the furanolactone 10 over three more steps. 

Terminal alkyne Grignard reagent (stronger acid) (stronger base)... 

An allylaluminum species, which was generated by the reaction of allyl Grignard reagent with diisobutylaluminum chloride, was found to react with terminal alkynes in... 

The CuBr-catalyzed reaction of a Grignard reagent with 1,2-allenyl ether in Et20 at 20 °C afforded terminal alkynes [53]. 

In the early 1980s, one of the first preparations of substituted allenes was reported, which employed a palladium-catalyzed cross-coupling reaction of allenyl halides [9]. In this study, allenyl bromides 13 and various Grignard reagents 14 were coupled in the presence of catalytic amounts of a Pd(0) species, generated in situ by reduction of a Pd(II) salt. Trisubstituted allenes 15 were obtained with high regioselectivity (allene 15 alkyne 16 = 90 10 to 99 1) (Scheme 14.5). 

Alkynes react with CF3SCI only via prior metallation with a Grignard reagent or CeHsLi (81) ... 

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