Insertion of alkyne and

Conjugated dienes were thus selectively obtained by hydrovinylation of alkynes catalyzed by a cationic ruthenium alkylidene complex [43] (Eq. 31). This reaction is thought to be promoted by the ruthenium hydride species resulting from the deprotonation of the <5-methyl group of the metallic precursor, followed by the sequential insertion of alkyne and ethylene into the metal-hydride and metal-vinyl bonds. 

Insertion of alkynes and perfluoroalkenes into the Re-H bond of (31) allows the preparation of /3-hydrogen-substituted vinyl and fluoroalkyl derivatives, Re C(CF3)=CH(CF3) (CO)5 and Re(CF2CHF2)(CO)s. 

RuC1(OCCR=CR C3H5)(CO)2]2 arising from insertion of alkyne and CO into an allyl-ruthenium bond [28],... 

The nickel-catalyzed carbonylation of allyl halides in the presence of alkynes and water produces 2,5-dienoic acids in good yields under very mild conditions (equation 25). This remarkable four-component reaction probably involves oxidative addition of the allyl chloride to the catalyst, followed by successive insertions of alkyne and CO, and finally hydrolysis. The carbon-carbon double bond derived from alkyne insertion is thus conjugated with the carbonyl group and generally has the (Z)-configuration. 

Trost and Toste explain their Pd(0)-catalyzed reaction by the following mechanism. First, reaction of Pd(0) and HCO2H generates hydridopalladium 38, and the vinylpalladium intermediate 39 is formed by insertion of alkyne, and either the... 

As noted in the introduction to this section, the insertions of alkynes and alkenes into metal-boron bonds appear to be involved in catalytic additions of borane reagents to alkenes and alkynes. One direct observation of the insertion of an alkyne into a metal-boron bond has been reported, and this reaction is shown in Equation 9.91. In another case, the reaction of an olefin with a metal-boryl complex generated products consistent with the... 

Anion (114), obtained from reaction of [HFe2(CO) l and PhC H CPh, undergoes insertion of alkyne and CO into the Fe-C... 

When the reaction of Ai-sulfonyl aryl aldimines and alkynes was carried out in the presence of 5 mol% of [RuCl2(p-cymene)]2, 20 mol% of AgSbFg, 10 mol% TsNH2 and 4 equiv. of AcOH in dioxane at 95°C, after 20 h, no isoquinoline derivative was obtained as for ketimines (Scheme 20), but indenamine derivatives were obtained instead resulting from C-H bond activation, insertion of alkyne, and C-C bond formation [(Eq. 104)] [196]. 

Scheme 7 Insertion of alkynes and alkenes with different orientations of heteroatom groups other isomers are also possible depending on the ligand environment (not shown)...

Scheme 1 Catalytic cycle for Type I mechanism comprising of protonolysis of M-X by REH, M-E insertion of alkyne, and protonolysis of M-Cvmyi by REH...

Similarly to alkenes. alkynes also insert. In the reaction of 775 carried out under a CO atmosphere in AcOH, sequential insertions of alkyne, CO. alkene. and CO take place in this order, yielding the keto ester 776[483]. However, the same reaction carried out in THF in the presence of LiCl affords the ketone 777, but not the keto ester[484]. The tricyclic terpenoid hirsutene (779) has been synthesized via the Pd-catalyzed metallo-ene carbonylation reaction of 778 with 85% diastereoselectivity as the key reaction[485], Kainic acid and allo-kainic acid (783) have been synthesized by the intramolecular insertion ol an alkene in 780, followed by carbonylation to give 781 and 782[486],... 

The insertion of alkynes into a chromium-carbon double bond is not restricted to Fischer alkenylcarbene complexes. Numerous transformations of this kind have been performed with simple alkylcarbene complexes, from which unstable a,/J-unsaturated carbene complexes were formed in situ, and in turn underwent further reactions in several different ways. For example, reaction of the 1-me-thoxyethylidene complex 6a with the conjugated enyne-ketimines and -ketones 131 afforded pyrrole [92] and furan 134 derivatives [93], respectively. The alkyne-inserted intermediate 132 apparently undergoes 671-electrocyclization and reductive elimination to afford enol ether 133, which yields the cycloaddition product 134 via a subsequent hydrolysis (Scheme 28). This transformation also demonstrates that Fischer carbene complexes are highly selective in their reactivity toward alkynes in the presence of other multiple bonds (Table 6). 

The proposed reaction mechanism (Scheme 7-2) comprises (1) oxidative addition of ArSH to RhCl(PPh3)3 to give Rh(H)(Cl)(SPh)(PPli3)n, (2) coordination ofalkyne to the Rh complex, (3) ris-insertion of alkyne into the Rh-H bond with Rh positioned at terminal carbon and H at internal carbon, (4) reductive elimination of 16 from the Rh(III) complex to regenerate the Rh(I) complex. 

This reaction typifies the two possibilities of reaction routes for M-catalyzed addition of an S-X (or Se-X) bond to alkyne (a) oxidative addition of the S-X bond to M(0) to form 94, (b) insertion of alkyne into either the M-S or M-X bond to provide 95 or 96 (c) C-X or C-S bond-forming reductive elimination to give 97 (Scheme 7-21). Comparable reaction sequences are also discussed when the Chalk-Harrod mechanism is compared with the modified Chalk-Harrod mechanism in hydrosily-lations [1,3]. The palladium-catalyzed thioboratiori, that is, addition of an S-B bond to an alkyne was reported by Miyaura and Suzuki et al. to furnish the cis-adducts 98 with the sulfur bound to the internal carbon and the boron center to the terminal carbon (Eq. 7.61) [62]. 

A nickel(O) complex catalyzes insertion of alkynes into cyclobutanones (Equation (79)).437 Formation of metalla-cycle 194 via oxidative cyclization of an alkyne with the carbonyl group of a cyclobutanone followed by /3-carbon elimination (formation of metallacycle 195) and reductive elimination are postulated for the mechanism (Scheme 92). 

The reaction mechanism was considered to be oxidative cyclization, and pal-ladacyclopentene 32 was formed. Reductive elimination then occurs to give cyclobutene 33, whose bond isomerization occurs to give diene 28. The insertion of alkyne (DMAD) into the carbon palladium bond of 32 followed by reductive elimination occurs to give [2+2+2] cocyclization product 27. Although the results of the reactions of E- and Z-isomers of 29 with palladium catalyst 26a were accommodated by this pathway, Trost considered the possibility of migration of substituents. Therefore, 13C-labeled substrate 25 13C was used for this reaction. 

A useful synthesis of alkynes and particularly of terminal ( )-enynes results from the insertion of the readily formed ( )-l,2-dichloro-l-lithioethene (68) into organozirconocene chlorides (Scheme 3.17). An intermediate ( )-2-chloroalkenyl zirconium species 69 undergoes anti-elimination of zirconocene dichloride to yield terminal alkynes 70 [38]. 

For the diboration reactions of alkynes catalyzed by Pt(0) complexes, the reaction mechanism involves the oxidative addition of diborane to the Pt(0) center, followed by the insertion of alkyne into the Pt-B bond and reductive... 

When the secondary amine 33 was used instead of a primary amine, a different type of three-component coupling reaction took place with aldehyde 34 and 1-alkynes 35 to afford the corresponding allylamines (36 and 37) [22]. In this reaction, Ir-hydride generated by amine (33) with Ir, would be a key intermediate. The reaction may proceed by addition of the Ir-hydride to the enamine derived from amine 33 and alkyne 34, followed by insertion of aldehyde and dehydration to give the coupling product (36 and 37). 

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