Synthesis of molybdenum imido alkylidene complexes and some reactions involving acyclic olefins

Schrock, Richard R.; Murdzek, John S.; Bazan, Gui C.; Robbins, Jennifer; DiMare, Marcello; O’Regan, Marie B.

doi:10.1021/ja00166a023

Cited by 1,142 publications

(711 citation statements)

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“…Preliminary studies examined the feasibility of this hypothesis for 1,4-stereocontrol (Scheme 2) through the examination of various substituents on silicon [9,10] and metal alkylidene catalysts, [11] as outlined in Table 1. Initial studies determined that the steric nature of the substituents on the silicon tether were indeed crucial in terms of silaketal construction, overall efficiency, and the level of diastereoselection, in which the diisopropylsilane proved optimal (Table 1; entry 3 versus 1 and 2).…”

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confidence: 99%

“…[12] Additional studies explored the effects of more reactive metal alkylidene catalysts, in which the second-generation Grubbs catalyst 11 and the molybdenum-based Schrock catalyst 12 proved significantly inferior for this particular transformation (Table 1; entries 4 and 5). [11] Table 2 summarizes the scope of the TST-RCM, under the optimized reaction conditions ( Table 1, entry 3). The construction of the mixed bisalkoxy silane 7 was achieved from the requisite allylic alcohol 4, through treatment with excess diisopropyldichlorosilane, to afford the monoalkoxychlorosilane 5, followed by the removal of the excess silylating agent and addition of the prochiral alcohol 6 (Scheme 2).…”

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confidence: 99%

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Diastereoselective Temporary Silicon‐Tethered Ring‐Closing‐Metathesis Reactions with Prochiral Alcohols: A New Approach to Long‐Range Asymmetric Induction

2003

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The ability to control stereochemistry in substrates where the reactive elements are distal represents a fundamentally important area of investigation that is commonly referred to as long-range asymmetric induction. [1,2] Although there are numerous examples of this phenomenon, a significant limitation with this type of process is the ability to predict the manner in which the chiral group attains proximity to the reactive site in order to translate stereochemical information. The inherent challenge associated with this requirement provided the incentive for the development of a new process where the elements of stereocontrol could be conserved in a predictable manner.[1,2] Herein, we describe a new approach to long-range asymmetric induction using the diastereoselective temporary silicon-tethered (TST) ringclosing-metathesis (RCM) reaction of mixed bisalkoxy silanes 1, derived from an allylic and prochiral alcohol, for the construction of cis-1,4-silaketals 2 (Scheme 1; n = 0). This methodology was also extended to higher homologues (where n=1-4), which resulted in the formation of the opposite trans diastereoisomer. [3][4][5][6][7][8] We envisioned that the TST-RCM of the mixed bisalkoxy silane 1 (Scheme 1; n = 0) should proceed through the favored transition state illustrated in Figure 1. The basis for this hypothesis was the assumption that the substituents (R') on silicon would result in nonbonding interactions with the pseudoaxial propenyl moiety in the disfavored transition state, and thereby prefer the formation of the cis-1,4-silaketal 2. The potential advantage of this approach is that the reactive elements involved in diastereoselection are conserved irrespective of ring size, which should translate into a convenient stereochemical relay, provided the relative orientation of the substituents is maintained in the medium rings. Moreover, the ability for ring-closing metathesis to facilitate the formation of medium and large rings should allow the application of this concept to higher homologues.

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Diastereoselective Temporary Silicon‐Tethered Ring‐Closing‐Metathesis Reactions with Prochiral Alcohols: A New Approach to Long‐Range Asymmetric Induction

2003

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“…115 Moreover, the molybdenum systems are known to react with acids, alcohols, and aldehydes, where the ruthenium complexes are stable to these functional groups. 137,145 However, the commonly used first and second generation ruthenium carbene systems 146,147 are not always an effective catalyst with substrates incorporating sulfides or amines. Conversion to the corresponding ammonium salts is sometimes necessary in the latter case for metathesis to occur.…”

Section: Closure Of Western Macrocyclementioning

confidence: 99%

Total Synthesis of (±)‐Haliclonacyclamine C

Smith

Sulikowski

2010

Angew Chem Int Ed

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“…A good possibility is successive "turnstile" operations in which three ligands rotate with respect to the other two. Mo complex 7b is analogous to 2b (Scheme 1); 10 2b also is exclusively an anti alkylidene THF adduct (δH α = 13.8 ppm in toluene-d 8 , J CH = 145 Hz). In stark contrast to the new alkylidene 7b, however, cooling the sample of 2b to −70 °C does not lead to splitting of the alkylidene resonance.…”

Section: Synthesis Of Alkylimido Mo-based Olefin Metathesis Catalystsmentioning

confidence: 99%

“…The solids were filtered off and the toluene solution was reduced to 5 mL. White solid was filtered after 48 hours at − 30 °C; yield 461 mg (0.55 mmol, 54%): 1 Variable temperature 1H NMR spectrum of a sample of 7b in toluene-d 8 . Two alkylidene resonances at −70 °C correspond to the two diastereomers of the anti THF adduct.…”

Section: Mo(nphad) 2 CL 2 (Thf) (10)mentioning

confidence: 99%

New Enantiomerically Pure Alkylimido Molybdenum-Based Alkylidene Complexes. Synthesis, Characterization, and Activity as Chiral Olefin Metathesis Catalysts

et al. 2007

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Molybdenum olefin metathesis catalysts that contain aliphatic 1-phenylcyclohexylimido (NPhCy) and 2-phenyl-2-adamantylimido (NPhAd) groups and (S)-Biphen or (R)-Trip)(THF) ligands (Biphen = 3,3′-di-tert-butyl-5,5′,6,6′-tetramethyl-1,1′-biphenyl-2,2′-diolate; Trip = 3,3′-bis(2,4,6-triisopropylphenyl)-2,2′-binaphtholate) have been prepared. Their catalytic activity and enantioselectivity in desymmetrization reactions such as ring-closing metathesis of amines and lactams and ring-opening/cross-metathesis of substituted norborneols with styrene were compared to the results obtained with the only known alkylimido catalyst Mo(NAd)(CHCMe 2 Ph)[(S)-Biphen]. The activities and enantioselectivities provided by these new chiral complexes vary significantly, but in virtually all instances explored were not superior to the adamantylimido analogs.

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Synthesis of molybdenum imido alkylidene complexes and some reactions involving acyclic olefins

Cited by 1,142 publications

References 0 publications

Diastereoselective Temporary Silicon‐Tethered Ring‐Closing‐Metathesis Reactions with Prochiral Alcohols: A New Approach to Long‐Range Asymmetric Induction

Diastereoselective Temporary Silicon‐Tethered Ring‐Closing‐Metathesis Reactions with Prochiral Alcohols: A New Approach to Long‐Range Asymmetric Induction

Total Synthesis of (±)‐Haliclonacyclamine C

New Enantiomerically Pure Alkylimido Molybdenum-Based Alkylidene Complexes. Synthesis, Characterization, and Activity as Chiral Olefin Metathesis Catalysts

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