Insertion route

Homoleptic lanthanide(III) tris(amidinates) and guanidinates are among the longest known lanthanide complexes containing these chelating ligands. In this area the carbodiimide insertion route is usually not applicable, as simple, well-defined lanthanide tris(alkyls) and tris(dialkylamides) are not readily available. A notable exception is the formation of homoleptic lanthanide guanidinates from... 

Metathetical reactions between NbCl4(THF)2, NbCls, TaCls, [(Et2N)2TaCl3]2, or (R2N)3Ta(=NBu (R = Me, Et) with various amounts of lithium amidinates have been employed to synthesize the corresponding heteroleptic niobium and tantalum amidinate complexes. The products were investigated as potential precursors to metal nitrides (cf. Section VI) Carbodiimide insertion routes... 

This is illustrated for a generalized hydrocarbon R2CH2 and its deuteriated counterpart R2CD2. If a mixture of these hydrocarbons reacts with a carbene exclusively by a direct insertion route, then the addition product will consist entirely of undeuteriated and dideuteriated compounds (13). 

Scheme 9. The asymmetric Rh-catalyzed C-H insertion routes to ritalin by Davies and Winkler (1999).

Aryl derivatives, l-Ar-l-GBnHn% were made in 3CM10% yields from BnH14 and arylhalocarbenes (generated from substituted benzal chlorides).83 A carbene insertion route to 7-CB10H13 was also reported for the reaction of B10H14 with CH2Br2 and NaH in 25% yield.84 85... 

Initially, one carbon atom (a methyl group) is attached to the metal of the catalyst (A in Figure 1). In the first step, it will capture and insert a propylene molecule via either 1,2- or 2,1-insertion route. Thus, one of these insertion events is stochastically chosen this choice, however, is not totally random but weighted by the probabilities of the two reactions. Here the relative probabilities are proportional to the relative rates. Now, if one assumes that the 1,2-insertion has happened in the first step, i.e. the iso-butyl group is attached to the catalyst (B) after insertion. At this stage four different elementary events are possible two alternative insertion routes (1,2- and 2,1-) proceeded by the capture of olefin, the termination reaction,... 

From alkyl complex p0, the olefin can be captured to form the Jt-complex TCo, and inserted via 1,2- or 2,1-insertion route. In the model applied here we consider the olefin capture and its insertion as one reactive event i.e. we assume a pre-equilibrium between the alkyl and olefin complexes, described by an equilibrium constant Kcompi = [icq] / [Pol = exp (AGcomp . / RT). This... 

The halogenated derivatives of six membered heterocycles, like their carbacyclic analogues, usually participate readily in coupling reactions that involve the incorporation of an olefin or carbon monoxide. The insertion of carbon monoxide commonly leads to the formation of either a carboxylic acid derivative or a ketone, depending on the nature of the other reactants present. Intermolecular and intramolecular variants of the insertion route are equally popular, and are frequently utilized in the functionalization of heterocycles or the formation of annelated ring systems. 

Had the phosphazide 5 been formed in the reaction of the thiatriazoles, then loss of nitrogen to form compound 6 would be the logical consequence. The authors therefore favor the direct insertion route without intervention of the (unknown) thioacyl azide, but no decisive choice can be made between alternative reaction mechanisms, since, if a compound 5 is actually formed from an open-chain thioacyl azide, it may rapidly cyclize to form the thermodynamically stable 4. 

There are two major routes to hydrocarbon production via gas phase ion-molecule reactions. These routes can be labeled C+ or C insertion (see Herbst, Adams, and Smith 1983, 1984) and condensation (see Mitchell and Huntress 1979, Walmsley et al. 1979, Winnewisser 1981, or Schiff and Bohme 1979). The insertion route for two-carbon hydrocarbons proceeds by reactions such as the following (Herbst, Adams, and Smith 1983, 1984) ... 

The insertion route to three-carbon-atom hydrocarbons proceeds via reactions such as ... 

The carbene insertion route (pathway (b)) has most frequently been implied to explain the thermal cydizations of various ethynyl-substituted aromatic precursors. Although the other two alternatives cannot be excluded at present, since in many cases (see below) no careful mechanistic studies have been undertaken, the carbene hypothesis has the advantage of... 

A carbene insertion route to the P-lactam fused cyclic enediyne (31) has been developed <02TL4241>. 

The azabicyclononane system is a common structural feature in diterpene alkaloids, and the nitrene insertion route to the ring system has been studied in detail in model decalins as well as in steroids (Scheme 11). Thus irradiation of the rrans-acyl azide (21) gave, in addition to isocyanate (30-33%), a mixture of Ae 7- and 8-lactams (22) and (23). The y-lactam (22) predominated, dthough the overall yield was poor. > The corresponding c/s-azide (24), however, gave the 8-lactam (25) as Ae major product, again in low yield. One elegant application of this type of intramolecular nitrene insertion reaction... 

In addition to the carbon monoxide insertion route, samarium acyl anions can also be prepared under reductive conditions by reaction of SmI with acyl halides. " In the absence of any other electrophiles, the acyl halides provide moderate yields of a-diketones (equation 77). The main by-product generated in these reactions is the a-ketol. 

Basak, A. Khamrai, U.K. Mallik, U. The synthesis and reactivity of novel azetidinyl enediynes. J. Chem. Soc. Chem. Commun. 1996, 749-750 Basak, A, Mandal, S. A carbene insertion route to P-lactam fused cyclic enediynes. Tetrahedron Lett. 2002, 43, 4241 4243 Banfi, L. Guanti, G, Synthesis of N-fused Lactendiynes , Eur. J. Org. Chem. 1998, 1543-1548,... 

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