Grubbs’ catalyst, intramolecular

Intramolecular [2+2+2] cyclotrimerizations of diynes and triynes possessing heteroatom tethers furnish benzoheterocycles. The cyclization of triynes 88 using the Grubbs catalyst 76 proceeds via cascade metathesis as shown in Eq. (35) to yield a tricyclic product 89 [88]. This novel type of catalytic alkyne cyclotrimerization can be applied to the cycloaddition of 1,6-diynes with monoalkynes [89]. 

Conformationally constrained a-Boc-aminophosphonates (387), (388) (389), (390) and (391) were made via a transition metal catalysed Curtins rearrangement. The conformational constraint involved either a ring-closing metathesis reaction catalysed by the first generation Grubbs catalyst or intramolecular cyclopropanation mediated by Rh2(OAc)4 (Figure 66). ... 

The remaining lone pair on carbon (which is not delocalized) can coordinate to Ru, just like the phosphine lone pair, giving a catalyst known as Grubbs IT (the second generation of the Grubbs T we made use of in the metathesis described above). In another widely used catalyst (known as the Hoveyda-Grubbs catalyst ) the second phosphine is also replaced by intramolecular coordination. 

In contrast, the cyclotrimerization catalyzed by the Grubbs catalyst involves consecutive intramolecular ring metathesis through carbene complexes or formation of a ruthenabicy-clo[3.2.0]heptatriene intermediate similar to that formed in the cobalt complex-catalyzed reaction. This mechanism is illustrated in Scheme 2 using acetylene as the alkyne source and CpRuCl[COD] as catalyst. 

Example 3, An intramolecular Buchner reaction within the Grubbs catalyst ... 

A flexible diversity-oriented synthesis (DOS) approach to a collection of tricyclic sultams is depicted in Scheme 2.21 [13f. The functionalized sultam scaffolds 52 and 55 embedding oxanorbornene units are readily derived by intramolecular Diels-Alder (IMDA) reactions. Domino ROM/RCM/CM transformations of these substrates using the Grubbs catalyst 2 with a set of co-olefins 53 gave rise to the desired heterocyclic systems 54 and 56, respectively, in good to very good yields. Interestingly, only one of the two epimers 55 participated in the RRM process. 

The ruthenium-carbene complex 8.52 is an excellent commercially available example of the Grubbs catalyst. However, intramolecular five-membered ring compounds 8.53-8.55, which are activated by coordination with an ether oxygen atom, are much more active with respect to electron-deficient olefins and are also stable with respect to air as shown in Fig. 8.2. 

Olefin metathesis is well-studied and offers a diverse catalogue of catalysts and synthetic opportunities. Coates and coworkers synthesized polymers functionalized with vinyl groups using a zinc-mediated alternating copolymerization technique. The polymers were subjected to olefin metathesis conditions using Grubbs catalyst, resulting in the formation of intramolecular 1,2-disubstituted olefin cross-links. ... 

Fully intramolecular [2 + 2 + 2] cyclization of triynes affords tricyclic products with complete chemo- and regioselectivity. Despite this advantage, this method is underdeveloped, which is probably due to the diminished accessibility of the triyne substrates. Peters and Blechert reported the first ruthenium-catalyzed fully intramolecular cyclotrimerization using the metathesis cascade strategy with Grubbs catalyst [23]. Later, Yamamoto et al. demonstrated that complex 6 efficiently catalyzes the cyclization of various triynes [14]. Examples of 1,6,11-triyne cyclization are summarized in Table 3.11. As an example, diether 58 (X = = O, R = H) underwent [2 + 2 + 2]... 

In 2014, an intramolecular atom transfer radical cyclisation (ATRC) between a trichloroacetamide and an anisole or enol acetate moiety was applied to the synthesis of highly functionalized 2-azaspiro[4.5]decanes or morphan compounds, respectively, using the second-generation Grubbs catalyst 20. The procedure was further employed to construct the azatricyclic framework of the immunosuppressant FR901483 by the elaboration of its azatricyclic core [eqn (7.15)]. 

Intramolecular [3+2] cycloaddition of ruthenium-alkenyl carbene complex a nonmetathetic behavior of Grubbs catalyst... 

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