Indium-based catalyzed reactions

A new method has been developed for the synthesis of ( )-3-methyl Baylis-Hillman-type adducts with high E/Z (>93%) selectivity in modest to good yields. The process consists of two steps an indium-mediated allylation reaction and a simple base-catalyzed isomerization step (Eq. 8.61). Various aldehydes were allylated with allyl bromides using indium under very mild conditions in aqueous media and thus converted to the Baylis-Hillman-type adducts.150... 

At a loading as low as 0.5 mol%, indium triflate catalyzes the three-component coupling reaction between aldehydes, amines, and Danishefsky s diene to afford tetrahydropyridine derivatives (Scheme 8.106) [138]. In fhe presence of indium triflate, 3,4-dihydro-2H-pyran reacts with in sitw-generated chromone Schiff s bases to give the endo cycloadducts (Scheme 8.107) [139]. 

N,iV-Disulfonyl ynamides react with salicylaldehydes through a keteni-mine intermediate in the presence of triethylamine giving access to 3-substituted iminosulfonylcoumarins (140BC3986). Biscoumarins fused at the pyrone ring arise from the indium(III) trifluoromethanesulfonate-catalyzed reaction of methyl coumarin-3-carboxylate with phenols, in good yields (14JOC8723). A library of 3,3 -biscoumarin-based protein kinase inhibitors is achieved from the condensation of 2 -hydroxyacetophenones... 

AUylation of the C-3 position of the cephem nucleus was accomplished by either indium mediated or indium trichloride promoted tin-mediated aUylation reactions in aqueous media. Both methods gave 3-allyl-3-hydroxycephams in moderate to exceUent yields.The synthesis of (E)-jS-methyl Baylis-Hillman adducts was obtained with high E/Z selectivity (> 93%) in modest to good yields by using an indium-mediated aUylation reaction foUowed by a simple base-catalyzed isomerization step (Eq. 4.23). ... 

The cyclotrimerization of alkynes catalyzed by transition metals is a general method for building substituted benzenes from aliphatic precursors. Multiple bonds are formed in these reactions in a single operation. Although the reaction of thermal trimerization relates to allowed electro-cyclic processes, it is catalyzed by several transition metals, such as Co, Ni, Rh, Pd, Rh, and Ru [38]. Most recent publications show promise for the participation of transition metal complexes in [2+2+2] cycloaddition reactions based on zirconium, titanium, and indium [9]. This reaction has synthetic potential for using metallocyclopentadienes as intermediates in the cyclotrimerization of alkynes. The reaction mechanism is shown in Scheme 2.1 [3, 38]. Two alkyne molecules coordinated to the metal, that is, complex 2.1, couple to form cyclopentadiene 2.2. Next there is either addition of the alkyne to the metallocycle 2.3 to form the metallocycle... 

In 10-2 M HC1, [In(tmpyp)]5+ has bands at 424 nm (e = 390,000), 518 nm (e = 3690), 558 nm (c = 23,200), and 597 nm (e = 4660). The spectrum is similar to that of indium(III)-tetraphenylporphyrin.16 The [In(tmpyp)]5+ is fully water soluble, and rapid acid solvolysis occurs only above 3 M HC1 levels. Refluxing a divalent metal chloride with H2tmpyp in water, and keeping the pH between 3 and 5, is the general method used to prepare the Cu2+, Zn2+, Ni2+, Mn3+, Fe3+, and Co3+ compounds.6 The 642-nm free-base porphyrin band disappears when the incorporation reaction is complete. The high-pH conditions (a) reduce the concentration of unreactive centrally protonated15 porphyrins, (b) minimize the extent of acid catalyzed metalloporphyrin solvolysis reactions,17 and (c) increase the concentration of the often more reactive hydrolyzed metal ion forms.18... 

Recently, extensive efforts have been made in the development of domino conjugate reduction/inter and intramolecular aldol reaction catalyzed by various metal complexes based on rhodium, iridium, cobalt, indium, nickel, and copper [22]. In 1999, Morken and Taylor [23] reported a rhodium-catalyzed conjugative reductive/aldol reaction between aldehyde and acrylate using QjMeSiH as reducing agent with a maximum diastereoselectivity of 23 1. 

Morphin sensors based on MIPs have also been described [432,439,441]. Amperometric morphine sensors based on morphin imprinted poly(3,4-ethylene-dioxythiophene), which catalyze morphine oxidation and lowers the oxidization potential on an indium tin oxide (ITO) electrode, is an example. The same MIP has been used in the form of immobilized molecular particles for the same purpose. In one report, rather uniform MIP microspheres were prepared through precipitation polymerization to produce more active surface area. Poly(3,4-ethylenedioxythiophene) was utilized to immobilize the MIP particles, prepared through the reaction between methacrylic acid monomers and trimethylolpropane trimethacrylate crossHnkers in the presence of morphin, on indium tin oxide (ITO) glass [441]. Another microfluidic amperometric MIP-based morphin sensing system, using 3,4-ethylenedioxythiophene monomers, has also been reported in the literature [439]. 

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