Synthesis of tethered

IV. First-Generation Approach Synthesis of Tethered Diacid 5... 

There are two ways to generate a collection of ligand molecules for immobilization on surfaces chemical library synthesis on micro- or macrobeads and diversity-oriented parallel synthesis of tethered unique compounds (Darvas et al., 2004). 

Intramolecular reactions of temporarily silicon-tethered molecules in synthesis of 0,Si-heterocycles 97S813. 

During studies directed towards the synthesis of spatol, Salomon and Murthi studied epoxysilane 153 bearing a temporary tether (Scheme 5.36), which circumvented the potential problem of configurational instability described above [57]. 

An unexpected varying regiochemistry in intramolecular benzannulation has also been observed in the synthesis of cyclophanes. As mentioned above, there are only two possible regiochemical outcomes in the benzannulation reaction, which differ in the direction of alkyne incorporation. / -Tethered vinyl-carbene chromium complexes undergo an intramolecular benzannulation reaction with incorporation of the tethered alkyne with normal regioselectivity to give meta-cyclophanes [28]. 

The selectivity for two-alkyne annulation can be increased by involving an intramolecular tethering of the carbene complex to both alkynes. This was accomplished by the synthesis of aryl-diynecarbene complexes 115 and 116 from the triynylcarbene complexes 113 and 114, respectively, and Danishefsky s diene in a Diels-Alder reaction [70a]. The diene adds chemoselectively to the triple bond next to the electrophilic carbene carbon. The thermally induced two-alkyne annulation of the complexes 115 and 116 was performed in benzene and yielded the steroid ring systems 117 and 118 (Scheme 51). This tandem Diels-Alder/two-alkyne annulation, which could also be applied in a one-pot procedure, offers new strategies for steroid synthesis in the class O—>ABCD. 

Thilgen C., Cardullo F., Haldimann R., Isaacs L., Seiler P., Diederich F., Boudon C., Gisselbrecht J. P., Gross M. Synthesis of Multiple Adducts of C60 With Specific Addition Patterns by Simple and Reversible (Templated) Tether-Directed Remote Functionalization Proc. - Electrochem. Soc. 1996 96-10 1260-1271 Keywords fullerene C60, regiochemistry... 

Keywords regio- and stereoselective silicon-tethered Diels-Alder cycloadditions, synthesis of branched sugars and linear and polycyclic hydrocarbons... 

In 1994, the same authors reported the synthesis of corresponding oxazolines tethered to sulfoxides by ortholithiation of the parent 2-phenyl oxazoline with butyllithium followed by addition of either (5)- or (/ )-/ -tolylmenthyl-sulfinate. Applied as ligands in the test reaetion, these diastereomerie ligands gave very different results, as shown in Seheme 1.25, thus demonstrating the... 

Synthesis of Polyethylene-tethered Phthalonitrile. Polyethylene monoalcohol ( 700 Daltons, 80% functionalized) in pellet form (6.0 g, 8.0 mmol) and anhydrous THF (62 mL) were added to a flask equipped with a magnetic stirring bar. This was allowed to stir for 2 hours before 4-nitrophthalonitrile (2.25 g, 13.0 mmol) was added to the mixture and the suspension heated to reflux. After the polymer had dissolved the CS2CO3 (4.22 g, 13.0 mmol) was added in three equal portions over 3 hours. After 24 hours the reaction was cooled to 60°C then poured into 500 mL of water with stirring. The precipitate was filtered and washed thoroughly with water until pH neutral. The product was then rinsed with A, V-DMF, THF and then dried under vacuum to yield 5.03 g of material. H NMR (toluene-dg, 100°C, 71% conversion) 5 6.86 (d), 6.59 (s), 6.41 (m), 3.41 (t), 3.37 (t), 1.31 (s), 0.88 (t). 

Synthesis of Tetrakis(polyethyleneoxy)phthalocyanine cobalt (II) (9). The polyethylene-tethered phthalonitrile (0.827 g, 1.0 mmol), 1,5-diazabicyclo [4.3.0] non-5-ene (0.062 g, 0.50 mmol) and cobalt acetate (0.044 g, 0.25 mmol) were added to a reaction vial equipped with a magnetic stir bar. The reaction was then heated to 175°C for 2 hours before reducing the temperature to 95°C and adding toluene. The reaction mixture was then poured into methanol, filtered, and the sohd washed further with methanol. The collected product was then dried under vacuum to yield... 

For conversion of amide to other acid derivatives, a novel synthesis of urea glycosides in aqueous media has been reported via the reaction of Steyermark s glucosyl carbamate with amines in good yields (Eq. 9.17).38 This method was successfully applied to develop a new route to the synthesis of urea-tethered neo-glycoconjugates and pseudooligosaccharides. 

Yu, K.M.K., Steele, A.M., Zhu, J Fu, Q.J. and Tsang, S.C. (2003) Synthesis of well-dispersed nanoparticles within porous solid structures using surface-tethered surfactants in supercritical CO2-Journal of Materials Chemistry, 13 (1), 130-134. 

The Pd°-catalyzed transformation of enediynes represents a highly efficient and effective approach for the synthesis of polycyclic compounds, with different ring sizes being obtained by a variation of the tether [129]. In this respect, reaction of 6/1-270 led to the tricyclic product 6/1-271 as a single diastereomer. The initial step is a chemoselective hydropalladation of the propargylic ester moiety in 6/1-270 to give an alkenyl-Pd-species, according to the mechanism depicted in Scheme 6.71. A hexatriene is formed as a byproduct. 

Hoveyda and coworkers [227] used a domino process to give chromanes 6/3-8 by treatment of 6/3-7 in the presence of ethylene. One of the first-generation Grubbs catalyst 6/3-9 and one of Blechert s [228] early examples allowed the synthesis of bicyclic compounds of different sizes, depending on the length of the tether thus, the reaction of 6/3-10 led to 6/3-11 using 30 mol% of the Schrock Mo complex 6/3-12. 

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