Room solid-supported

Microwave irradiation has been used to accelerate the Gewald reaction for the one-pot synthesis of N-acyl aminothiophenes on solid support [67]. A suspension of cyanoacetic acid Wang resin 35, elemental sulfur, DBU and an aldehyde or ketone 36 in toluene was irradiated for 20 min at 120 °C in a single-mode microwave synthesizer (Scheme 13). Acyl chloride 37 was added, followed by DIPEA, and the mixture was irradiated for 10 min at 100 °C. After cooling to room temperature, the washed resin was treated with a TEA solution to give M-acylated thiophenes 38 in 81-99% yield and purities ranging from 46-99%. 

Similarly, a solid-supported imide has been reported to serve as an acylating reagent under microwave conditions by Nicewonger and coworkers [130], The starting imide was immobilized on aminomethyl polystyrene and in this case benzoyl chloride was chosen to prepare the acylating reagent (Scheme 7.111). Primary amines and piperazines were smoothly acylated at room temperature, but more hindered secondary amines required more time and higher temperatures, and anilines... 

Bis(indolyl)nitroethanes are obtained readily in 7-10 min in high yields (70-86%) on fine TLC-grade silica gel (5-40 pm) by Michael reaction of 3-(2 -nitrovinyl) indole with indoles. The same reaction reported requires 8-14 h for completion at room temperature [77]. Several functionalized resins have been prepared from Merrifield resin via a MW-assisted procedure that utilized mixed solvent system to facilitate the swelling of resins and coupling with microwaves [78], These resins can function as solid supports or polymeric scavengers in solid phase synthesis. 

In addition to the aforementioned microwave-assisted reactions on solid supports, several publications also describe microwave-assisted resin cleavage. In this context it has been demonstrated that carboxylic acids could be cleaved from conventional Merrifield resin, using the standard TFA-DCM 1 1 mixture, by exposure of the polymer-bound ester and the cleavage reagent to microwave irradiation in a dedicated Teflon autoclave (multimode instrument). After 30 min at 120 °C, complete recovery of the carboxylic acid was achieved (Scheme 12.9) [26]. At room temperature, however, virtually no cleavage was detected after 2 h in 1 1 TFA-DCM. 

Under certain conditions phosphorescence can be observed at room temperature from organic molecules adsorbed on solid supports such as filter paper, silica and other chromatographic supports. 

Notwithstanding the excellent analytical features inherent in molecular phosphorimetric measurements, their use has been impeded by the need for cumbersome cryogenic temperature techniques. The ability to stabilize the "triplet state" at room temperature by immobilization of the phosphor on a solid support [69,70] or in a liquid solution using an "ordered medium" [71] has opened new avenues for phosphorescence studies and analytical phosphorimetry. Room-temperature phosphorescence (RTF) has so far been used for the determination of trace amounts of many organic compounds of biochemical interest [69,72]. Retention of the phosphorescent species on a solid support housed in a flow-cell is an excellent way of "anchoring" it in order to avoid radiationless deactivation. A configuration such as that shown in Fig. 2.13.4 was used to implement a sensor based on this principle in order to determine aluminium in clinical samples (dialysis fluids and concen-... 

The use of enzymes as biocatalysts for the synthesis of water-soluble conducting polymers is simple, environmentally benign, and gives yields of over 90% due to the high efficiency of the enzyme catalyst. Since the use of an enzyme solution does not allow the recovery and reuse of the expensive enzyme, well-established strategies of enzyme immobilization onto solid supports have been applied to HRP [22-30]. A recent work reported an alternative method that allows the recycle and reuse of HRP in the biocatalytic synthesis of ICPs. The method is based on the use of a biphasic catalytic system in which the enzyme is encapsulated by simple solubilization into an IL. The main strategy consisted of encapsulating the HRP in room-temperature IPs insoluble in water, and the other components of the reaction... 

The coalescence of atoms into clusters may also be restricted by generating the atoms inside confined volumes of microorganized systems [87] or in porous materials [88]. The ionic precursors are included prior to irradiation. The penetration in depth of ionizing radiation permits the ion reduction in situ, even for opaque materials. The surface of solid supports, adsorbing metal ions, is a strong limit to the diffusion of the nascent atoms formed by irradiation at room temperature, so that quite small clusters can survive. 

Sodium salts of carboxylic acids, including hindered acids such as mesitoic, rapidly react with primary and secondary bromides and iodides at room temperature in dipolar aprotic solvents, especially HMPA, to give high yields of carboxylic esters.679 The mechanism is Sn2. Another method uses phase transfer catalysis.680 With this method good yields of esters have been obtained from primary, secondary, benzylic, allylic, and phenacyl halides.681 In another procedure, which is applicable to long-chain primary halides, the dry carboxylate salt and the halide, impregnated on alumina as a solid support, are subjected to irradiation by microwaves in a commercial microwave oven.682 In still another method, carboxylic acids... 

The working electrodes found to be useful at room temperature can also be used at low temperature. There are no special constraints. Platinum is probably the most widely used, simply because it is the most common electrode material for room-temperature work. A mercury electrode can also be employed, either as a hanging mercury drop electrode (HMDE) [23], a thin mercury film on a solid support, or an amalgam [26]. The HMDE was reported to extend the range of usable potentials to somewhat more negative values than found with platinum [23]. Of course, below -39°C, the HMDE is actually a solid electrode however, no detectable change in its voltammetric behavior is noted at the phase transition. 

The synthetic procedure developed by Usyatinsky involves pre-absorbing the mixture of acidic support and ammonium acetate (ammonia source) with an ether solution of the starting materials, evaporating the solvent and heating the solid residue in a domestic microwave oven for 20 min (Scheme 5.21). After irradiation, the reaction mixture was allowed to cool to room temperature and was then washed with a mixture of acetone and triethylamine to extract the product from the solid support. No yields were quoted but the purities of the products were quoted to be 75-85%. 

To a solution of substituted hydrazides 2 (0.02 mol) in ethanol added inorganic solid support (10 g) at room temperature. Similarly inorganic support (8 g) was added in the solution of phenacyl bromide/4-chlorophenacyl bromide/4-amino phenacyl bromide 1 (0.01 mol) in dichloromethane. Adsorbed material was mixed properly, kept inside alumina bath and subjected to microwave irradiation for 60-120 s. On completion of the reaction as followed by TLC examination, the mixture was cooled to room temperature and then product was extracted into ethanol (2x15 mL). The filtrate was concentrated and recovering the solvent under reduced pressure afforded the product which was purified through recrystallization from ethanol-DMF mixture. 

Cobb et al.30 constructed 4-amino-2-carboxy-6-chloroquinazolin-4-one on a solid support using the 2-carboxylic ester linkage as the resin point of attachment. The quinazolinone (43) was converted to the resin-bound 4-chloroquinazoline (44) with SOCl2. The chloro group was then displaced even with anilines under acid-catalyzed conditions at room temperature. Finally, the resin-bound quinazoline-2-carboxylic ester (45) was cleaved from the resin and decarboxylated with TMSCl/Nal (Fig. 8) (yield 69%, purity 95%). 

Last, but not least, full application of QDs in chemical sensors would require the immobilization of the nanoparticles into appropriate solid supports in order to develop reliable active phases (able to provide, for instance, convenient fiber optic-based sensing applications). Although only a few reports have been published so far regarding the trapping of the QDs in solid matrices, some important steps have already started towards the realization of the potential of these technologies. There is still plenty of room for further development in all those directions. 

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