Second generation Grubbs

Scheme 5.29 Cycloisomeiisation of 1,6-allenes catalysed by Grubbs second generation catalyst...

A similar strategy served to carry out the last step of an asymmetric synthesis of the alkaloid (—)-cryptopleurine 12. Compound 331, prepared from the known chiral starting material (l )-( )-4-(tributylstannyl)but-3-en-2-ol, underwent cross-metathesis to 332 in the presence of Grubbs second-generation catalyst. Catalytic hydrogenation of the double bond in 332 with simultaneous N-deprotection, followed by acetate saponification and cyclization under Mitsunobu conditions, gave the piperidine derivative 333, which was transformed into (—)-cryptopleurine by reaction with formaldehyde in the presence of acid (Scheme 73) <2004JOC3144>. 

Ring-closing metathesis of diene 318 with a Grubbs second-generation catalyst gave 2,5-dihydropyrrole 319 (Equation 56). The absolute stereochemistry was assigned based on single crystal X-ray diffraction analysis... 

Gmbbs has described a chiral ruthenium-based catalyst and has illustrated its application to enantioselective desymmetrization. The catalyst is a derivative of Grubbs second-generation dihydroimidazolinylidene-containing catalyst with the chirality derived from diphenylethanediamine in the carbene backbone. Substrate 90 undergoes ringclosing metathesis in 90% ee on treatment with this catalyst and Nal ... 

As described above in Eq. 43, simple allylboronates can be transformed into more elaborated ones using olefin cross-metathesis. " Treatment of pinacol allylboronate 31 with a variety of olefin partners in the presence of Grubbs second-generation catalyst 142 smoothly leads to formation of 3-substituted allylboronates 143 as cross-metathesis products (Eq. 104). Unfortunately, these new allylic boronates are formed as mixtures of geometrical isomers with modest E/Z selectivity. They are not isolated but rather are treated directly with benzaldehyde to give the corresponding homoallylic alcohol products in good yields (Table A). 

Grubbs second generation complex was found to polymerize acetylene to give mostly /r< / i--polyacetylene whose conductivity was lO S cm after doping. ... 

Pawlow et al. (3) prepared multifiinctionalized high-trans-content elastomeric polymers using Grubbs second-generation ruthenium catalyst in the metathesis polymerization of cyclooctadiene, cyclopentene, and l,4-bis(trimethoxysilyl)-2-butene. 

Fig. 3 Olefin metathesis catalysts Schrock tungsten (Cl) and molybdenum (C2) alkylidene complexes, Grubbs first- (C3) and second-generation (C4) catalysts, Hoveyda-Grubbs second-generation catalyst (C5), and Grubbs third-generation catalyst (C6)...

RCM of l-allyl-2-(vinyloxy)benzenes using Grubbs second generation catalyst 37 provides 4//-chromenes in excellent yield (Equation 54) <2003TL311, 2005T9996>. 

Allyl-l-(allyloxymethyl)-3-isopropoxy-4-methoxybenzene 149 can undergo a one-pot ruthenium catalyzed isomerization followed by RCM in the presence of Grubbs second generation catalyst 37 to afford 5-isopropoxy-6-methoxy-1 //-isochromcnc (Scheme 48) <2003SL1859>. 

Grubbs second generation catalyst can effectively catalyze the RCM of 2-vinylphenyl acrylates 670 to afford coumarins in high yields (Equation 270) <2003TL4199>. 

The [l,6]benzo- and [l,6]pyrido-diazocines 78 were obtained by one-pot procedure via isomerization-RCM of the diene 76 in the presence of the Grubbs second-generation catalyst 77 (Scheme 11) <2004TL9171>. Although the number of literature examples describing isomerization-RCM is still limited, this concept has... 

The sulfone and sulfoxide alkenes 134 underwent the RCM reaction in the presence of Grubbs second-generation catalyst 77 (see Scheme 11, Section 14.06.3.4.1) to form the corresponding 1,4-thiazocines 135 and 136 (Scheme 15) <2004JOC2750>. Sulfanyl derivatives 134 (X = S) were inactive in this transformation and did not produce the... 

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