Nickel-catalyzed reactions derivatives

Tamao and Ito have reported a nickel-catalyzed protocol for the cyclization/hydrosilylation of 1,7-diynes to form (Z)-silylated dialkylidene cyclohexane derivatives.For example, reaction of 1,7-octadiyne with triethoxysilane catalyzed by a mixture of Ni(acac)2 (lmol%) and DIBAL-H (2mol%) in benzene at 50°G for 6h gave the corresponding silylated dialkylidene cyclohexane in 70% yield as a single isomer (Table 1). The reaction of 1,7-octadiyne was also realized with mono- and dialkoxysilanes, trialkylsilanes, and dialkylaminosilanes (Table 1). Diynes that possessed an internal alkyne also underwent nickel-catalyzed reaction, albeit with diminished efficiency (Table 1), while 1,6- and 1,8-diynes failed to undergo nickel-catalyzed cyclization/hydrosilylation. 

These palladium- or nickel-catalyzed reactions are radical reactions leading to an organometallic product. By using a precursor such as 37 as a 1 1 mixture of diastereoisomers, the palladium-catalyzed cyclization provides in a stereoconvergent way the cyclopentylmethylzinc derivative 38 which, after allylation, produces the unsaturated ester 39 in 71% yield". The intermediate radical cyclizes via a transition state A where all the substituents are in an equatorial position. Interestingly, the analogous reaction using Ni(acac)2 as a catalyst allows the preparation of heterocyclic compounds such as 40. The... 

Negishi, E., Van Horn, D. E. Selective carbon-carbon bond formation via transition metal catalysis. 4. A novel approach to cross-coupling exemplified by the nickel-catalyzed reaction of alkenylzirconium derivatives with aryl halides. J. Am. Chem. Soc. 1977, 99, 3168-3170. 

DeaUylation. The nickel-catalyzed reaction is applicable to a wide range of amines, 5-membered A-heteroaromatic compounds, amides, and sulfonamides. Ally ether cleavage is also facile and selective (with TBS, Bn, MOM, THP, Ac, Bz, Piv, An, and prenyl derivatives of alcohols intact). ... 

Derivation (1) From natural gas by absorption or adsorption. (2) From coal mines for use as fuel gas. (3) From a mixture of carbon monoxide and hydrogen (synthesis gas) obtained by reaction of hot coal with steam the mixed gas is passed over a nickel-based catalyst at high temperature. See methanation. Methane can also be obtained by a nickel-catalyzed reaction of carbon dioxide and hydrogen. (4) Anaerobic decomposition of manures and other agricultural wastes. (5) By horizontal drilling of coal seams. 

Nickel-catalyzed reaction of 1,3-dienes with vinyldisilane is notable [57]. In addition to an acyclic diene, 1,4-bis-silylation of a cyclic diene is also achieved to give cyclic allylsilane derivatives 62 as a mixture of cis and traris isomers (Eq. 29). 

Nickel-catalyzed reaction of 1,2-dihydrotetramethyldisilane with various internal alkynes affords silole (silacyclopentadiene) derivatives 90 in good yields (Eq.46) [54]. 

Recent application of the nickel-catalyzed reaction with diyne 91 provides new effective access to functionalized silole derivatives 92, which are further utilized for the synthesis of silole-thiophene co-polymers (Eq.47) [84]. 

Bicyclopropylidene (7), a special MCP derivative with a geminal disubstitution at the alkene, is also capable of forming a [2 + 2] cycloadduct, even with an only moderately strain-activated alkene such as cyclobutene, in a nickel-catalyzed reaction. Cycloocta-1,5-diene is formed as the second major poduct, presumably as a cyclobutene dimerization product. ... 

Whereas palladium(0)-catalyzed reactions of dialkyl fumarate and dialkyl maleate yield reaction products identical to those obtained from the phosphane-modified nickel-catalyzed reactions (vide supra), analogous palladium(0)-catalyzed reactions with ( )-but-2-enoic or (E)-cinnamic acid derivatives lead to different products to the nickel-catalyzed reactions, i.e. in the palladium-catalyzed reactions formal distal cleavage of but-2-enoic MCP occurs to provide methyl tra i-2-methyl-4-methylenecyclopentanecarboxylate (12, R = Me) and methyl trans-4-methylene-2-phenylcyclopentanecarboxylate (12, R = Ph), respectively." Yields and stereoselectivities are slightly higher with palladium(O) catalysts. When R = Me, 7.4% of the C-C double bond isomerization product, methyl traM -2,4-dimethylcyclopent-3-enecarboxylate (13, R = Me), is additionally obtained, raising the combined yield of cyclocodimers to 49.9%. With methyl (jE )-cinnamate, analogous isomerization only occurs upon workup, i.e. distillation of the crude product. 

All products from the nickel-catalyzed reaction of allylic systems with alkynes can be derived from two main intermediates. The course of the reaction is dependent on the solvent, however, by appropriate choice of the reaction conditions, good yields of cyclopentenones can be attained in some cases38-39. 

In contrast, 3,3-dimethoxycyclopropene does not react stereospecifically with this pair of olefins under similar conditions. Both alkenes provide the [2 + 1] cycloadduct with tram-positioned ester functions11. Interestingly, the reaction of 3,3-dimethoxycyclopropene with methyl propenoate preferentially produces the tram-substituted vinylcyclopropane derivative under very mild conditions. Therefore, the thermal and the nickel-catalyzed reactions of 3,3-dimethoxycyclopropene are complementary in terms of simple diastereoselectivity (vide supra). 

In recent years Ishikawa and coworkers have described some very complex photochemical rearrangements of compounds derived from nickel-catalyzed reactions of silacyclopropenes with silylalkynes. As depicted in equation 93, it was shown that the disilacyclohexadiene A could be photochemically converted to the same products as were formed from the silacyclobutene B. In the absence of a trapping reagent the silaindene C was formed as a major product, via the proposed intermediates shown141. In the presence of methanol, two adducts were isolated whose structures can be understood in terms of the reaction of methanol with one of the proposed intermediates. While the structures of the products are confirmed by the X-ray crystal structure data, the mechanisms of the reactions observed must be considered speculative at this time. 

Notably, the nickel-catalyzed decarbonylative cycloaddition affords a regioisomer opposite to that formed in the palladium-catalyzed Larock heteroannulation [21], For example, the nickel-catalyzed reaction of anthranilic acid derivatives 39 with l-trimethylsilyl-2-phenylacetylene (43) affords indole 44 with phenyl substituents at the 2-position [Scheme 12.18(a)], whereas the palladium-catalyzed reaction... 

Nickel-catalyzed reactions involving [2+2+2] cycloaddition of 1,6-diynes 2.171a,b to phenylallene gave 1,3-dihydroisobenzofuran derivatives 2.172a,b in good yields, 63% and 72%, respectively... 

Evans has disclosed an enantioselective nickel-catalyzed reaction of enolates and orthoesters, as depicted in Scheme 3.30 [110]. In contrast to the titanium enolates described in Equation 11, nickel enolates, such as 199, were not sufFiciently nucleophilic to enable direct reaction with trimethyl orthoformate. The use of BFj OEt2 as an activating agent leads to the corresponding oxonium ion derived from trimethyl orthoester, which can be trapped by en-olate 199. Under these reaction conditions, 197 is converted into alkylated product 200 in 98% ee and 91 % yield. 

It has been reported that nickel catalyzed the reactions of 6-amino-1,3-dimethyluracil with substituted alkynylketones in water to give substituted 2,4-dioxopyrido[2,3-f/ pyrimidine derivatives in quantitative yields at room temperature (Eq. 4.70).134 The products have potential pharmacological and biological activities. The reaction may have proceeded through an ionic process. 

Development of new methodologies for formation of carbon-carbon bonds has been one of the major tasks in organic chemistry. Obviously, organometallic compounds, particularly zinc derivatives, have found great use in such reactions. During the past several years, there have been several significant reports of nickel- and palladium-catalyzed reactions of dialkylzincs and alkylzinc halides with alkyl halides of diverse structure. A detailed account of most of these studies can be found in a recent review by Knochel et al,246... 

The nickel-catalyzed [4 + 4]-cycloaddition of butadiene to form cyclooctadiene was first reported by Reed in 1954.90 Pioneering mechanistic and synthetic studies largely derived from the Wilke group advanced this process to an industrially important route to cyclodimers, trimers, and other molecules of interest.91-94,943 95,96 While successful with simple dienes, this process is not useful thus far with substitutionally complex dienes as needed in complex molecule synthesis. In 1986, Wender and Ihle reported the first intramolecular nickel-catalyzed [4 + 4]-reaction of... 

The SiCaC reaction of 5-hexyn-l-al 23 gives the corresponding 2-(exo-silymethylene)-l-cyclopentanol 24 in high yield (Scheme 7.11) [20]. The reaction is accelerated by gem-disubstitution for example, the reaction of 3,3-gem-disubstituted 5-hexyn-l-al 23 (X = C(C02Et)2, C(CH20Me)2) is substantially faster and cleaner than the unsubstituted derivative (X=CH2), which is accompanied by a small amount of silylformylation product [21]. It should also be noted that the formation of l-siloxy-2-methylenecyclopentane is not observed, in sharp contrast with the nickel-catalyzed version of this reaction [20]. 

---