Mortreux catalyst system

A particularly interesting example is the synthesis of alkyne-bridged oligomers and polymers, which are attractive materials for optical and electronic applications. Bunz and coworkers were able to modify the Mortreux catalyst system [Mo(CO)6 and a suitable phenol]11 and reaction conditions to perform acyclic alkyne metathesis of 1,4-dipropynylated benzenes to produce high-molecular-weight poly(p-... 

The Mortreux catalyst system has shown extraordinary versatility in PPE synthesis, as shown in Scheme 6.4. In this case, PPEs generated by the ADIMET of 1,4-dipropynylbenzenes with the Mo(CO)6/4-chlorophenol system are characterized by polymers of very high molecular weight The upper limit... 

Scheme 6.5 Copolymers generated with the Mortreux catalyst system.

Stephens-Castro coupling of 12a generated 14a in 4.6% isolated yield [62]. Almost 30 years later, Bunz reported the preparation of 14b from 13b in 6% yield with the Mortreux catalyst system, clearly demonstrating the potential of alkyne metathesis for the preparation of macrocycles [63]. However, isolation of the desired [6]cycle from linear polymers was reported to be rather tedious. In 2004, the preparation was reported of 14b from 13b in 61% yield with EtC=Mo[N(Ar)(CMe3)]3/4-nitrophenol in 1,2,4-trichlorobenzene at 1 mmHg [59]. 

ADIMAC has been utilized in the formation of many other types of novel macrocycHc scaffolds. VoUhardt reported the preparation of o-phenylene ethynylene macrocycles 21 with the Schrock catalyst (Me3CO)3W=CCMe3 in moderate yield (Scheme 6.11) [67]. Notable here was the unreactivity of monomers containing substituents ortho to the alkynes. The Mortreux catalyst system was utilized in the preparation of macrocycles from monomer 22 containing a disiloxane hinge (see Scheme 6.12). A mixture of macrocycles 23 and 24 was isolated in moderate yield [68]. One particularly impressive example of the use of ADIMAC to prepare large, extended r-systems (Scheme 6.13) was reported by Haley this was based... 

The specificity of biphase catalyst systems (in conjunction with activities comparable to those anticipated with single-phase systems) has been illustrated in an elegant way by Mortreux et al. [24] In a regioselective hydro-formylation of methyl acrylate to give alpha-formylpropionic acid with the catalyst [HRh(CO)(TPPTS)3], these authors observed an aldehyde yield comparable to that achieved with TPP, as well as an alpha/beta product ratio of the expected order of magnitude and an even higher turnover frequency (TOF) (Scheme 2). 

Two recent studies have examined the selective monoalkylation and polyaUcylation of sucrose (Scheme 17, 52). Using Pd(acac)2/Ph3P, sucrose was efficiently polyalkylated with butadiene in 4 1 isopropanol/water to give a mixture of 2,7-octadienyl ethers averaging 4-5 ether linkages per sucrose.While conditions for polyalkylation were found, Mortreux and co-workers also reported an alternative set of conditions that favor selective monoaUcylation.t Treatment of sncrose (52) with Pd(OAc)2/3 TPPTS (TPPTS = tris(m-sulfonatophenyl)phosphine) in 5 2 isopropanol/1 M NaOH (80 °C, 30 min, 73% conversion) afforded a 2 1 mixture of mono- and diethers, from which monoethers 53a (65%) and 53b (18%) were isolated. The reaction is of interest for its selective alkylation, the use of a water-soluble catalyst system, and the observation that NaOH acts as a strong activator for the reaction. 

Mortreux and co-workers compared the activity of the SAPC catalysts with that of the homogeneous analogue in the hydroformylation of methyl acrylate [69]. They observed an activity for the SAPC that was strongly dependent on the amount of water present in the system. More remarkably, the optimised activity of the SAPC was higher than that of the homogeneous systems. This effect was ascribed to the polar interactions between the substrate and the silica support. This effect was not observed for nonpolar substrates such as propene, which supported the hypothesis. 

Alkyne metathesis is a curious reaction in view of the fact that two alkyne triple bonds are cleaved and reconstructed simultaneously leading to different triple bonds. The first reported effective catalyst is a heterogeneous mixture of tungsten oxide and silica. Then Mortreux found that a catalytic system that consisted of Mo(CO)6 and resorcinol was effective for alkyne metathesis. As reported, the added alkynes come into equilibrium with different product... 

Wacker oxidation of olefins to ketones catalyzed by palladium complexes is a well-known process which has been applied to numerous olefins [120]. However, selective oxidation of Cg-Cig a-olefins remains a challenge. Recently, Mortreux et al. have developed a new catalytic system for the quantitative and selective oxidation of higher a-olefins in an aqueous medium [121-123]. For example, 1-decene was oxidized to 2-decanone in 98% yield using PdS04/ H9PV6M06O40/CUSO4 as the catalyst in the presence of per(2,6-di-0-methyl)-j9-cyclodextrin, which probably played the role of a reverse phase transfer reagent [Eq. (22)]. 

Furthermore, a vast number of organometallic catalyzed reactions can be performed in a biphasic manner thus proving that also uncommon reactions may be worth to be investigated in liquid/liquid systems. For instance, Braddock describes the atom economic nitration of aromatics in a two-phase process [192], Nitration of aromatics leads usually to excessive acid waste streams and the classical Lewis acid catalysts such as boron trifluoride are destroyed in the aqueous quench after the reaction thus making any recycle impossible. In the method of Braddock the ytterbium triflate catalyst is solved in the aqueous phase and can be recycled by a simple evaporative process. Monflier and Mortreux [193] investigated the nickel catalyzed isomerization of olefins, for instance allylbenzene, in a two phase system yielding good yields of cis- and trans-methylstyrene. 

This predictability is not hmited to benzene monomers. The 3,6-dialkynylcarba-zole 9, which has an approximately 90° angle between alkynes, leads to the square [4]cycle as the major product gram-scale preparation under precipitation-driven conditions provides the [4]cycle in excellent yield [61]. The use of well-defined catalysts is required, as use of the Mortreux system yields linear polymers with only trace amounts of the [4]cycle [53]. These macrocycles have found considerable utility in nanofibril-based explosives-detection devices [56, 65, 66]. 

AiPter Noyori s discovery, related semisandwich catalysts based on ruthenium-arene complexes were developed and applied to the ATH of 2-propanol to carbonyl substrates. In this line, Mortreux and co-workers (282) developed the Ru(arene)(/3-amino alcohol) system (Fig. 71) and isolated and characterized... 

Reversible and fast chain transfer is a prerequisite in order to control a polymerization process. In this regard, relative amount and synergy between each catalytic partner, that is, precatalyst and cocatalyst/CTA, are of primary importance. This was the case with ethylene, which has been by far the most studied monomer in this frame, as shown by Gibson [9] with Fe/Zn catalysts, after the pioneering studies of Mortreux [8] with Ln/Mg and more recently Kempe with Y/Al systems [40]. 

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