Bose reaction

Over the years the literature is filled with examples where the initial characterization was incorrect. One example is illustrated below. In 1940, Sethna and Shah presumed that they synthesized coumarins 42 and 43 from a reaction between P-orcacetophenone (44) and its 4-0-methyl ether 45 under standard Kostanecki-Robinson conditions, respectively. Three decades later Bose and Shah synthesized coumarin 43 via another route and concluded that the initial assignment made by Sethna and Shah was incorrect. After the Bose and Shah findings were published, Ahluwalia and Kumar concluded that the Sethna and Shah products were actually chromones 46 and 47 based on proton NMR data and chemical derivatization. Despite these shortcomings, the Kostanecki-Robinson reaction remains an effective method for formation of both coumarins and chromones. 

MW heated reactions in homogeneous media, using either neat reagents or in the presence of solvents, may also be performed at atmospheric pressure. This approach has been used particularly by Bose et al. [17]. (MORE Chemistry), who reported, for example, the rapid synthesis of heterocycles [18] in open vessels. Another approach, which avoids hazards due to the flammability of solvents, is to perform the reactions under reflux in a MW oven, which is modified to allow the reaction vessel to be attached to a reflux condenser outside the MW oven [7, 19]. It should be pointed out, however, that most of the available evidence shows that rate enhancements of MW heated reactions in homogeneous media at atmospheric pressure are small or nonexistent [19], This will be discussed in more detail later in this review (see also Chapt. 5 of this book). 

A number of syntheses of heterocycles were performed using the MORE technique [17, 18]. While most of these reactions had been reported in Organic Synthesis to require reflux times of an hour or more, Bose et al. were able to obtain comparable yields in a matter of minutes. For example, benzimidazole 18 was synthesized from 1,2-diaminobenzene 17 and formic acid, which served as both reagent and solvent, in 70% yield in 3 min (Scheme 4.10), compared with the recommended heating time of 2 h [17]. 

In some of these syntheses the original reaction conditions were modified and this might partly account for the much shorter reaction times. The synthesis of phthalimidoacetic acid 20 from phthalic anhydride 18 and glycine in the presence of triethylamine (Scheme 4.11) gives a yield of 83-90% when the reagents are heated under reflux in toluene for 1.5 h [29]. Bose found that good yields of the product could be obtained in 1-3 min when the reaction was performed in DMF in a MW oven [18]. 

This reaction was later re-examined by Westaway and Gedye [30], who showed that the rate of the reaction was actually the same whether performed by MW heating or conventional heating in DMF at the same temperature. Thus the rate increase observed by Bose was due to an increase in polarity and temperature when DMF was substituted for toluene. 

Bose et al. [18] reported that the Knoevenagel reaction between salicylaldehyde 27 and ethyl malonate 28 in the presence of piperidine gave a high yield of 3-carbethox-ycoumarin 29 in 3 min in an open vessel in a MW oven (Scheme 4.15). 

Also, Bose et al. [76] have shown that the steric course of /J-lactam formation can be influenced by the MW heating rate. For example, in the reaction of the benzoylox-yacetyl chloride 53 with the Schiff base 54 (Scheme 4.28) the cis adduct 55 is the main product at low irradiation power whereas high power favors the formation of the trans adduct 56. Lactams of this type can serve as intermediates for the side chain oftaxol and its analogs. 

Bose et al. [77] compared a similar reaction of the acid chloride of tetrachlor-ophthaloyl glycine 57 with a Schiff base under MW irradiation and conventional... 

Microwave organic reaction enhancement (MORE) chemistry was described by Bose as a safe and convenient alternative to pressure reactions and modified microwave ovens [20]. 

In 1991 Bose described the synthesis of ot-vinyl /1-lactams by reaction of ,/l-unsa-turated acyl chlorides with a Schiff base in chlorobenzene under microwave irradiation (an example of the eco-friendly MORE chemistry, in which only a limited amount of solvent is used) [20b]. Under these conditions, a-vinyl /1-lactam formation can be achieved in 65-70% in approximately 5 min (classical conditions require several hours and lead only to modest yields). 

This methodology has also been used by Bose, who described the synthesis of the thienamycin side chain [119], the first step of which was a [2+2] cycloaddition under microwave irradiation. Likewise, Khajavi described the reaction of trichloroacetic anhydride with imines [120] with classical heating the reaction requires the use of Fe2(CO)9 as a catalyst, whereas under microwave irradiation a catalyst is not required. 

Bose has described reactions between acid chlorides 214 and Schiff bases 215 where the stereoselectivity depends on the order of addition of the reagents (Scheme 9.68) [117]. When the condensation was conducted by a normal addition sequence (i.e. acid chloride last), only the cis /1-lactam (216b) was formed. However,... 

Deoxynucleotides for DNA synthesis are made at the nucleoside diphosphate level and then have to be phosphorylated up to the triphosphate using a kinase and ATP. The reducing equivalents for the reaction come from a small protein, thioredoxin, that contains an active site with two cysteine residues. Upon reduction of the ribose to the 2 -deoxyri-bose, the thioredoxin is oxidized to the disulfide. The thioredoxin(SS) made during the reaction is recycled by reduction with NADPH by the enzyme thioredoxin reductase. 

This enzyme [EC 2.4.2.14], also known as glutamine phosphoribosyl-pyrophosphate amidotransferase, catalyzes the reaction of glutamine with S-phospho-a-D-ri-bose 1-diphosphate and water to produce 5-phospho-)3-D-ribosylamine, diphosphate (or, pyrophosphate), and glutamate. 

Bose DS, Sudharshan M, Chavhan SW (2005) New protocol for Biginelli reaction-a practical synthesis of monastrol. Arkivoc 228-236... 

This extension of the Smith analysis, involving methylation of the polyalcohol, has been studied in detail by Bose, both on model systems and on the Ti fructan.84 When a ffuctan is used, this method may give l-hydroxy-3-methoxy-2-propanone and l,3-dimethoxy-2-propa-none, together with methylated glycerols. These compounds may react further under methanolysis conditions to yield 2,5-dimethoxy-2,5-bis(methoxymethyl)-l,4-dioxane and l,3-dimethoxy-2-propanone dimethyl acetal, respectively. Several of these compounds may be obtained from sucrose by a model reaction. In view of the wide variety of hydroxy compounds obtained in this study,84 their separation and identification as benzeneboronates was investigated, and certain of the latter derivatives were purified by gas-liquid chromatography. The characterization of 1,2- and 1,3-diols by the mass spectra of their cyclic benzeneboronates has also been described.634... 

Although we have described metabolic transformations in plant cells in terms of individual pathways, these pathways interconnect so completely that we should instead consider pools of metabolic intermediates shared among these pathways and connected by readily reversible reactions (Fig. 20-37). One such metabolite pool includes the hexose phosphates glucose 1-phosphate, glucose 6-phosphate, and fructose 6-phosphate a second includes the 5-phosphates of the pentoses ri-bose, ribulose, and xylulose a third includes the triose phosphates dihydroxyacetone phosphate and glycer-aldehyde 3-phosphate. Metabolite fluxes through these... 

A procedure similar to the condensate separation in the imperfect Bose gas was employed by Lifshitz and Pitaevski [78]. The diagrammatic technique allows us to calculate the reaction rate and steady-state joint correlation functions. A separation of a condensate from terms with k = 0 cannot be done without particle production (p = 0), in which case nA, tiq —> 0 as t —> oo. In this respect the formalism presented by Lushnikov [111] for the non-stationary processes is of certain interest. 

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