Insertion double

A interesting and useful reaetion is the intramolecular polycyclization reaction of polyalkenes by tandem or domino insertions of alkenes to give polycyclic compounds[l 38]. In the tandem cyclization. an intermediate in many cases is a neopentylpalladium formed by the insertion of 1,1-disubstituted alkenes, which has no possibility of /3-elimination. The key step in the total synthesis of scopadulcic acid is the Pd-catalyzed construction of the tricyclic system 202 containing the bicyclo[3.2. Ijoctane substructure. The single tricyclic product 202 was obtained in 82% yield from 201 [20,164). The benzyl chloride 203 undergoes oxidative addition and alkene insertion. Formation of the spiro compound 204 by the intramolecular double insertion of alkenes is an exam-ple[165]. 

The phosphido complex, Th(PPP)4 [143329-04-0], where PPP = P(CH2CH2P(CH2)2)2) has been prepared and fully characterized (35) and represents the first actinide complex containing exclusively metal—phosphoms bonds. The x-ray stmctural analysis indicated 3-3-electron donor phosphides and 1-1-electron phosphide, suggesting that the complex is formally 22-electron. Similar to the amido system, this phosphido compound is also reactive toward insertion reactions, especially with CO, which undergoes a double insertion (35,36). 

Bis(cyclopentadienyl)zirconium 1,3-alkadiene complexes19-20 show interesting stepwise double insertion reactions to carbonyl compounds, exploration with respect to their stereochemical features has only just begun21-23. 

The reaction of methyl acrylate and acrylonitrile with pentacarbonyl[(iV,iV -di-methylamino)methylene] chromium generates trisubstituted cyclopentanes through a formal [2S+2S+1C] cycloaddition reaction, where two molecules of the olefin and one molecule of the carbene complex have been incorporated into the structure of the cyclopentane [17b] (Scheme 73). The mechanism of this reaction implies a double insertion of two molecules of the olefin into the carbene complex followed by a reductive elimination. 

A related unprecedented double insertion of electron-deficient alkynes has also been reported in the reactions of the linear Pt2Pd heterotrimetallic complex 64 with 65 (RO2CCSCR) (Scheme 24) [95,96]. A series of unsymmetri-cal A-frame clusters 68 has thus been obtained in which a first insertion of the alkyne takes place site-selectively into the Pt-Pd bond vs the Pt-Pt bond (66). After a zwitter-ionic polar activation of the resulting inserted alkene (67), a subsequent reaction with the phosphine unit of the dpmp allows one to obtain the products 68 via the nucleophilic migration of the terminal P atom from the Pd center to the CH terminal carbon (formation of the P-C bond). 

Reactions of the Ir1 complexes (289) and (290) with H2 and subsequent reaction of the dihydride products with dimethyl acetylenedicarboxylate, Me02CC CC02Me (dma), give the Ir11 complexes (291), (292), (293), and (294), as shown in Reaction Scheme 26.482 The X-ray crystal-structure determination of (294) confirms the double insertion of the alkyne into each of the Ir—H bonds of (293). 

If one employs o-iodoaniline derivatives in this double insertion chemistry, 2-quinolones are generated in good yield after a basic work-up to remove the nitrogen protecting group (Scheme 14).15... 

Insertions of isocyanide into niobium-carbon bonds follow a path similar to that with vanadium, resulting in the formation of the 7]2-iminoacyl complexes, which can then be involved in further chemistry.175 176 The reaction of acetone with cyclopentadienyl complex 110 under a carbon monoxide atmosphere gives the if -acetone compound 111. Complex 111 subsequently undergoes either stepwise insertion of two isocyanides via 112 or double insertion of the isocyanide to give complex 113 (Scheme 48).177... 

Reaction of an allene with stannylborane 9 in the presence of a palladium catalyst results in the double insertion of 1,1-dimethylallene into the tin-boron bond, affording the 1 2 adduct 18 (74% GC yield) along with the 1 1 adduct (18% GC yield) (Equation (103)) 227... 

Many alkyl carbenoids insert into saturated and unsaturated zirconacycles to afford zirco-nacydohexanes and -hexenes 126, which give the expected products 127 upon hydrolysis (Scheme 3.30) [48,50,68], There should be comparable scope for further elaboration of the six-membered zirconacycles, as has already been established for the five-membered analogues. Yields are generally high, one exception being the insertion of lithiated chloroace-tonitrile into saturated zirconacycles, where double insertion predominates [50],... 

Insertion of phenyl, trimethylsilyl, and nitrile-stabilized metalated epoxides into zircona-cyclcs gives the product 160, generally in good yield (Scheme 3.37). With trimethylsilyl-substituted epoxides, the insertion/elimination has been shown to be stereospecific, whereas with nitrile-substituted epoxides it is not, presumably due to isomerization of the lithiated epoxide prior to insertion [86]. With lithiated trimethylsilyl-substituted epoxides, up to 25 % of a double insertion product, e. g. 161, is formed in the reaction with zirconacyclopentanes. Surprisingly, the ratio of mono- to bis-inserted products is little affected by the quantity of the carbenoid used. In the case of insertion of trimethylsilyl-substituted epoxides into zirconacydopentenes, no double insertion product is formed, but product 162, derived from elimination of Me3SiO , is formed to an extent of up to 26%. 

DOUBLE INSERTION IN REACTIONS OF GLYCINE DERIVATIVES REARRANGEMENT OF SYMMETRICAL ANHYDRIDES TO PEPTIDE-BOND-SUBSTITUTED DIPEPTIDES... 

FIGURE 7.34 Decomposition of the symmetrical anhydride of A-methoxycarbonyl-valine (R1 = CH3) in basic media.2 (A) The anhydride is in equilibrium with the acid anion and the 2-alkoxy-5(4//)-oxazolone. (B) The anhydride undergoes intramolecular acyl transfer to the urethane nitrogen, producing thelV.AT-fcwmethoxycarbonyldipeptide. (A) and (B) are initiated by proton abstraction. Double insertion of glycine can be explained by aminolysis of the AA -diprotected peptide that is activated by conversion to anhydride Moc-Gly-(Moc)Gly-0-Gly-Moc by reaction with the oxazolone. (C) The A,A -diacylated peptide eventually cyclizes to the IV.AT-disubstituted hydantoin as it ejects methoxy anion or (D) releases methoxycarbonyl from the peptide bond leading to formation of the -substituted dipeptide ester. 

Reaction of a cis/trans mixture of 2,5-dimethyIfuran with dichlorocarbene produces a mixture of the mono and disubstituted derivatives, in 40 and 47% overall yields, respectively [8], This appears to be the only example of a double insertion of the carbene into two CH bonds of a single molecule. 

The factors that control the strictly alternating copolymer chain with no detectable errors (e. g., microstructures involving double insertion of ethene) have been the object of detailed studies since the discovery of the first Pd" catalysts for the alternating alkene/CO copolymerisation [11]. Sen was the first to demonstrate that double carbonylation is thermodynamically unfavorable and to suggest that the higher binding affinity of Pd" for CO relative to ethene inhibits multiple ethene insertions, even in the presence of very low concentrations of CO [12]. Therefore, once a palladium alkyl is formed, CO coordination ensures that the next monomer will be a CO molecule to generate the acyl complex. 

Dibromotetrachloroethane reacts with la in the presence of PPh3 and yields the dibromides [l]15a and [2]15a in 31% and 21% yields, respectively"5, or only 2]15a in 14% yield117. In contrast, dibromotetrafluoroethane yields a mixture of the two oligomers [n 28 and a double insertion product 29118 (equation 16). The bromide [2]15a has also been... 

A notable double insertion of methylacetylene into the methylene bridge has been observed with the classical -y-lactone-type cobalt complexes 1. The heterocyclic methylene ligand (CRR ) originally attached to both metal centers is displaced by the new alkylidene ligand ju.-C(CH3)— C(H)=C(CH3)—C(H)=CRR (116, 122) (Scheme 28a other ligands omitted for clarity). This example also points to the possibility of methylene homologation in the coordination core of a catalyst (see Section IX). 

Recently, double insertion of CO into the reactive thorium-silicon bond of Cp2 ThSiR3(Cl) allowed the isolation of the first metalloxy ketene complex 14. Reactivity studies of complex 14 are described in Scheme 939. 

A double insertion of carbon monoxide has been observed for the amine-induced reaction of alkynes with dodecacarbonyltriiron leading to cydobutenediones (Scheme 1.7) [28]. 

Reactions of monomeric and dimeric rhodium(II) porphyrins with carbon monoxide - As already reported in Sect. 3.3, a carbonylrhodium(II) porphyrin behaves as an acyl radical. Hence, if possible, dimerization or coupling reactions occur. Evidence for the formation of isomeric 2 1 Rh(P) CO adducts, namely a monoadduct of the dimer and a metallo ketone complex, and a dimeric 1 1 adduct in the reaction of [Rh(OEP)]2 with carbon monoxide according to sequences (38) and (39) has been presented [340,341] solution equilibria and structures have been studied essentially by lHNMR, 13CNMR, and IR spectroscopy. The first half of sequence (38) and reaction (39) occurred in parallel at CO pressures up to 12 atm at 297 K. At higher pressures, or at lower temperatures, the double-insertion of CO shown in the last step of (38) was observed. 

Murakami, M. Masuda, H. Kawano, T. Nakamura, H. Ito, Y. Facile synthesis of vicinal di- and tricarbonyl compounds by Sml2-mediated double insertion of isocyanides into organic halides./. Org. Chem. 1991, 56,1-2. 

Suginome et al. discovered that the use of Ni(acac)2 and DIBAL-H as a reductant results in the double insertion of alkynes 280 across the B-Si bond in silaborane 281 to afford silaborated butadienes 282-284 (acac = acetylaceto-nate). NMR experiments revealed the stereoselective formation of head-to-head dimerization product 282 as the... 

This procedure is apparently limited to cyanomethylcopper derivatives, copper amides, heteroarylcopper compounds, and copper thiolates. Use of bis(iodomethyl)-zinc, (ICH2)2Zn, results in products from double insertion. 

Zincate carbenoids. Reaction of lithium trialkylzincates with a 1,1-dibro-moalkane results in a double insertion into the C-Br bonds to provide a secondary zincate carbenoid.2 These products undergo Pd-catalyzed coupling with acid chlorides or vinyl bromides. 

Under conditions similar to those for allyl halides, 1,4-dichlorobutene reacts with nickel carbonyl to give butadiene. However, a double insertion of acetylene and carbon monoxide can be successfully carried out using 4-chloro-2-buten-l-ol and generating hydrogen halide in situ with a weak acid inorganic halide combination, e.g., NaBr-H3P04 (58). 

Samarium-mediated functionalization also occurs in the case of N=N bonds [287]. A high yield (80%) double insertion of carbon monoxide into the N=N... 

A recent discovery has been the unprecedented double insertion of isocyanides into 1,4-dihydropyridines, bearing an electron-withdrawing group at the 3-position, resulting in the formation of substituted benzimidazolium salts 298 (Scheme 68) <2007AGE3043>. 

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