Tandem Mo-catalyzed

Catalytic Asymmetric Synthesis Through Tandem Mo-Catalyzed... 

Catalytic Asymmetric Synthesis through Tandem Mo-Catalyzed AROM/RCM... 

Scheme 17. The tandem Zr-catalyzed kinetic resolution and Mo-catalyzed conversion of styrenyl ethers to chromenes is used in the first convergent and enantioselective total synthesis of the antihypertensive agent (S,R,R,R) nebivolol...

Scheme 19. Mo-catalyzed RCM in tandem with catalytic hydrogenation allows the control of C2-C6 relative stereochemistry in the macrolactam region of Sch 38516...

Scheme 8. Mo-catalyzed tandem ARCM can be used to synthesize seven-membered carbo-and heterocyclic structures efficiently and in optically enriched form...

In contrast to 52 (Scheme 12), diastereomer 55 (Scheme 13), because of its more exposed and highly reactive strained olefin, undergoes rapid polymerization in the presence of 4a. The less reactive Ru complex 56 [23] can however be used under an atmosphere of ethylene to effect a tandem ROM/CM to generate 57. The resulting triene can be induced to undergo Mo-catalyzed ARCM (5 mol % 4a) to afford optically pure 58, the AROM/RCM product that would be obtained from 55. 

Scheme 16. Mo-catalyzed tandem AROM/CM proceeds with high enantioselectivity and olefin stereocontrol...

Scheme 17. Mo-catalyzed tandem AROM/CM delivers highly functionalized cyclopentanes in the optically pure form...

During the same year, both an acid-catalyzed [60] and a TiCl4-catalyzed [61] ortho-alkylation of anilines with styrene were published, but offering only a very low selectivity. The reaction of anisole and styrene catalyzed by Mo(CO)6 [62] afforded the corresponding branched diaryl product with a comparable yield and selectivity as shown by our protocol. Furthermore, Michelet and coworkers successfully employed substituted styrenes in a gold-catalyzed tandem Friedel-Crafts-type addition-carbocyclization reaction [63]. 

It was found that molybdenum hexacarbonyl effectively catalyzes a tandem Claisen rearrangement—cyclization reaction of allyl aryl ethers 173 to produce the dihydrobenzo-furans 174 in goocl yields (equation 80) . However, the methallyl aryl ethers 175 under the same conditions (40 mol% of catalyst Mo(CO)g in refluxing toluene for 55 hours) gave good yields of the corresponding 2,2-dimethylchromans 176 (equation 81) . 

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