Grubbs II catalyst

Another example of an efficient domino RCM is the synthesis of the highly functionalized tricyclic ring system 6/3-72 by Hanna and coworkers [252], which is the core structure of the diterpene guanacastepene A (6/3-73) (Scheme 6/3.21) [253]. Reaction of 6/3-71 in the presence of 10 mol% of Grubbs II catalyst 6/3-15 led to 6/3-372 in 93 % yield. Interestingly, the first-generation Ru-catalyst 6/3-13 did not allow any transformation. 

Another intramolecular ene-yne metathesis followed by an intermolecular metathesis with an alkene to give a butadiene which is intercepted by a Diels-Alder reaction was used for the synthesis of condensed tricyclic compounds, as described by Lee and coworkers [266]. However, as mentioned above, the dienophile had to be added after the domino metathesis reaction was completed otherwise, the main product was the cycloadduct from the primarily formed diene. Keeping this in mind, the three-component one-pot reaction of ene-yne 6/3-94, alkene 6/3-95 and N-phenylmaleimide 6/3-96 in the presence of the Grubbs II catalyst 6/3-15 gave the tricyclic products 6/3-97 in high yield (Scheme 6/3.28). 

Other -substituted and reduced 2-azepinone derivatives 22 can also be accessed in high yields (Table 3) by ring closing metathesis on the precursors 21 using Grubbs II catalyst 18. A variety of IV-heteroaryl substitutent groups were tolerated in this reaction <06TL3295>. 

A compact approach to the 1-phosphonylated 2-benzazepine 56 was achieved based on a ringclosing metathesis reaction on 55 using Grubbs II catalyst <06SL2771>. 

A chiral [4]pseudocatenane 16 was synthesized from chiral triptycene-based /m( crown ether) and three equivalents of hw[p-(but-3-enyloxy)benzyl]ammonium salt in CH2CI2 in the presence of Grubbs II catalyst, followed by reduction <06CEJ5603>. Several novel calix[4]arenocrowns were prepared by a simple one-pot reaction of calix[4]monohydroquinone diacetate with bw-tosylates, e.g. l,4-bw[2-(2-(2-(2-tosyloxy-ethoxy)ethoxy)ethoxy)ethoxy)benzene, in dry MeCN in the presence of NaOH the self-assembly into calix[4]areno[2]catenanes with a dicationic salt and />-bfr(bromomethyl)-benzene was also demonstrated <06TL6012>. 

Singh and Han [60] have reported the preparation of another dihydropyrrole by using a N-Cbz derivative obtained by decarboxylative amidation (Scheme 9.27, results line 1) as starting material. N-Alkylation with allyl bromide followed by RCM (Grubbs II catalyst) furnished the dihydropyrrole in excellent yield (95%). Lee et al. have similarly transformed the amination product (Table 9.2, entry 21) into a variety of N-heterocycles [54]. 

RCM to afford compound 21 (Scheme 6). Although Grubbs II catalyst afforded compound in moderate yield (64%), only the dimerization product could be obtained using Grubbs I catalyst (10 mol% Grubbs I, PhMe, reflux, 16 h, 37% of dimerization product of 21, 6% of expected product 21). 

Ring closing metathesis mediated by Grubbs II catalyst in a type c ring construction process has been used to access stereoisomeric 1,2-disubstituted tetrahydroazepine-3-ol derivatives preparation of the required diene precursor started from an optically pure substituted aziridine carboxylate ester <2007T3321>. 

The second intermediate, a 6 -<9-acroyl 6-0-allyl-dialkene was subjected to RCM (with Grubbs II catalyst) and afforded small amounts of the C2-sym-metrical derivative, accompanied by E- and Z-cyclic monomers.316... 

N-Dienv11richIoroacetamide 174 (11 = 0, R=H) was, however, subsequently also subject to tandem RCM/ATRC catalyzed by the Grubbs II catalyst 175 (Fig. 43) [254]. The yield of 177 in this reaction was reported to be 82-91%, showing that catalyst 175 is also effective in such tandem processes. Tandem cross-metathesis/ ATRC reactions of N- a 11 v 11 ri c h I o ro acetamides with styrenes catalyzed by 175 produced rather low yields of trichlorinated lactams [254]. Almost at the same time Schmidt and Pohler reported similar tandem RCM/ATRC sequences of 1,6-dienyl trichloroacetates with 5 mol% of 175 and of 1,7-dienyl trichloroacetates... 

Within this chapter, two sections are devoted to rhodium and ruthenium. The two main procedures using rhodium are first, the fonnation of 1,3-dipoles from diazocompounds followed by a 1,3-dipolar cycloaddition [10] and second, hy-droformylation [11]. The ruthenium-catalyzed domino reactions are mostly based on metathesis [12], with the overwhelming use of Grubbs I and Grubbs II catalysts. 

Isomerization of the C-allyl glycoside 302 provides the corresponding C-(l-propenyl) derivative 303 as a major E-isomer. Cross metathesis proceeds in high yield only with the Grubbs II catalyst to deliver the homodimer 304, transformed to C-disaccharide analog 305 of the mycobacterial motif. 

At the end of a metathesis reaction treatment with NCCH2COOK in MeOH renders the Grubbs II catalyst inactive by transforming it into 7. ... 

Cross-metathesis reactions. The valuable cinnamylation reagent and other homologous allylation reagents are readily accessible from cross-metathesis using the Grubbs II catalyst ... 

Grubbs II catalyst does not lose activity during cross-metathesis of co-alkenols with I-alkynes. ... 

The cause of the failure of the Grubbs II catalyst to achieve cross-metathesis of vinyl chloride is ascribed to the rapid elimination of HCl from the chlorovinyldene carbenoid or the exchange of the chlorine atom into a CysP group. ... 

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