Sequential ethyl 2-

In a certain country with an emerging economy, a governmental decision has been made to establish a polymer industry based on native resources. No oil refineries or coal tar operations exist. Cotton (pure cellulose) and sugar are the major raw materials. In addition, electrolytic processes can be used, since hydroelectric power abounds. Your first step is to set up plants to produce from sugar, sequentially ethyl alcohol, acetic add, and butadiene. Erom electrolysis you now have NaOH, CI2, HCN, and HCl. Sulfuric and nitric acids are also produced locally. 

Hydroxycortisone BMD) (48) A solution of 4 g of 17a,20 20,21-bis-methylenedioxypregn-4-ene-3,l 1-dione (cortisone BMD) (46) dissolved in 300 ml of t-butanol and 5 ml of water is treated with 34 ml of 35 % hydrogen peroxide and 0.45 g of osmium tetroxide predissolved in 36 ml of /-butanol. The resulting mixture is allowed to stand at room temperature for 2 days. Diol (47) which crystallizes during the reaction is collected by filtration and washed with /-butanol and water. The filtrate is diluted with ethyl acetate and washed sequentially with aqueous sodium chloride, aqueous 10% sodium bisulfite, aqueous 10% sodium bicarbonate and finally with water to neutrality. The solvent is evaporated and a second crop of the diol (47) is collected, providing a total of about 3.8 g. 

Bond density surfaces are also superior to conventional models when it comes te describing chemical reactions. Chemical reactions can involve many changes in chemica bonding, and conventional formulas are not sufficiently flexible to describe what happen (conventional plastic models are even worse). For example, heating ethyl fonnate t( high temperatures causes this molecule to fragment into two new molecules, foraii( acid and ethene. A conventional formula can show which bonds are affected by ths reaction, but it cannot tell us if these changes occur all at once, sequentially, or in soms other fashion. 

Another acylated ampicillin derivative with expanded antimicrobial spectrum is piperacil1 in (19). Its synthesis begins with 1-ethyl-2,3-diketopiperazine (j7, which itself is made from ]i-ethylethylenediamine and diethyl oxalate), which is activated by sequential reaction with trimethylchlorosilane and then trichloromethyl chioroformate to give This last... 

The synthesis of key intermediate 12, in optically active form, commences with the resolution of racemic trans-2,3-epoxybutyric acid (27), a substance readily obtained by epoxidation of crotonic acid (26) (see Scheme 5). Treatment of racemic 27 with enantio-merically pure (S)-(-)-1 -a-napthylethylamine affords a 1 1 mixture of diastereomeric ammonium salts which can be resolved by recrystallization from absolute ethanol. Acidification of the resolved diastereomeric ammonium salts with methanesulfonic acid and extraction furnishes both epoxy acid enantiomers in eantiomerically pure form. Because the optical rotation and absolute configuration of one of the antipodes was known, the identity of enantiomerically pure epoxy acid, (+)-27, with the absolute configuration required for a synthesis of erythronolide B, could be confirmed. Sequential treatment of (+)-27 with ethyl chloroformate, excess sodium boro-hydride, and 2-methoxypropene with a trace of phosphorous oxychloride affords protected intermediate 28 in an overall yield of 76%. The action of ethyl chloroformate on carboxylic acid (+)-27 affords a mixed carbonic anhydride which is subsequently reduced by sodium borohydride to a primary alcohol. Protection of the primary hydroxyl group in the form of a mixed ketal is achieved easily with 2-methoxypropene and a catalytic amount of phosphorous oxychloride. 

Although it may not be obvious, putative intermediate 12 could conceivably be fashioned in one step from lactol 13. Of course, 13 can be regarded as a latent aldehyde that should be amenable to an a-chelation-controlled carbonyl addition reaction21 with ethyl-magnesium bromide. This event could secure the formation of the indicated stereocenter in intermediate 12. It seems reasonable to suppose that the sequential action of aqueous acid and 1,1-... 

Dichlorocarbene, generated by the action of 50 % potassium hydroxide on chloroform, adds to ethyl 1 W-azepine-l-carboxylate to furnish the all /rntu-trishomoazepine 12 in 35% yield280 (see Houben-Weyl, Vol. E 19b, p 1523). Subsequently, and as a result of a careful and detailed study of the addition of dichlorocarbene generated by the thermal decomposition of phenyl(trichloromethyl)mercury, it was deduced that carbene addition takes place sequentially in the order C4 —C5, C2—C3 and C6 — Cl. The intermediary mono- 10 and bis(dichlorocar-bene) 11 adducts have been isolated and characterized. 

On heating with sodium borohydride in glacial acetic acid. 5//-dibenz[/t,/ azepine (5) undergoes sequential acylation and reduction to yield 5-ethyl-5/7-dibcnz[A,/ ]azepine (8, R = Et).192 Similarly, reduction in trifluoroacetic acid produces the trifluoroethyl derivative 8 (R = CF3CH2 61% mp 69-70 C).193... 

To 0.89 g (4.0 mmol) of (45>,55>)-2-ethyl-4,5-dihydro-4-melhoxymelhyl-5-phenyloxazole and 0.52 g (4.0 mmol) of cthyldiisopropylaminc in 10 rnL of Et20 arc added 1.08 g (4.0 mmol) of 9-borabicyclo[3.3.1]nonyl trifluo-romethanesulfonate30 in a dropwise fashion at — 78 C under nitrogen. The mixture is stirred for 2 h at — 78 °C and 4.0 mmol of the aldehyde are added dropwise at — 78 °C. Stirring is continued at this temperature for 3 h then 20 mL of CH,OH, 9 raL of pH 7 phosphate buffer and 9 mL of 30% H202 are added sequentially. After 45 min at 0 C, workup as described for the anti-esters furnishes 4,5-dihydro-2-(2-hydroxy-l-methylalkyl)-4-methoxymethyl-5-phenyloxazoles 18 as oily products. Without further purification, the crude adducts are heated to reflux in 4.5 N sulfuric acid for 12-14 h. Isolation of the 3-hydroxy esters follows the procedure for an -3-hydroxy esters (vide supra). 

There are no proven examples of 1,2-hydrogen atom shifts this can be understood in terms of the stereoelectronie requirements on the process. The same limitations are not imposed on heavier atoms (e.g. chlorine). The postulate309 that ethyl branches in reduced PVC are all derived from cbloroethyl branches formed by sequential 1,5-intramolecular hydrogen atom transfers as described for PE (Section 4,4.3.1) has been questioned.,6,6 It has been shown that many of these ethyl branches are derived from dichloroethyl groups. The latter are formed by sequential 1,2-chlorine atom shifts which follow a head addition (Section 4.3.1.2). 

Treatment of N-benzoyl-L-alanine with oxalyl chloride, followed by methanolic triethylamine, yields methyl 4-methyl-2-phenyloxazole-5-carboxylate 32 <95CC2335>. a-Keto imidoyl chlorides, obtained from acyl chlorides and ethyl isocyanoacetate, cyclise to 5-ethoxyoxazoles by the action of triethylamine (e.g.. Scheme 8) <96SC1149>. The azetidinone 33 is converted into the oxazole 34 when heated with sodium azide and titanium chloride in acetonitrile <95JHC1409>. Another unusual reaction is the cyclisation of compound 35 to the oxazole 36 on sequential treatment with trifluoroacetic anhydride and methanol <95JFC(75)221>. 

Figure 2. Thin-layer radiochromatogram of urine (100 il) from rats injected with labeled PbTx-3. TLC plates were developed in two sequential solvent systems chloroform ethyl acetate ethanol (50 25 25 80 10 10). Radioactive zones were scraped and counted in a liquid scintillation counter. Native PbTx-3 runs at 13 cm.

In a preliminary report, Ross et al. [40] used affinity chromatography to identify a putative bovine renal brush border Na /H exchanger. Brush border membranes were solubilized with Triton X-100 and chromatographed sequentially over lentil lectin Sepharose 4B and 5-(A-benzyl-iV-ethyl)amiloride coupled to epoxy-activated Sepharose 6B. The eluant contained 178- and 146-kDa proteins that were susceptible to Endo-F. Moreover, the eluants reacted on dot blot immunoassays with antisera to a 20-amino acid peptide of a human Na /H exchanger vide infra). The relationship between these proteins and the 66-kDa protein previously identified by the same investigators using amiloride photolabeling is presently unclear. 

Transfer the sample to the column. Rinse the sample flask sequentially with 5 mL, 5 mL, and then 10 mL of hexane-ethyl acetate (4 1, v/v). Allow each rinse to drain to the top of the sodium sulfate layer before adding the next portion. Discard the accumulated eluant, place a 100-mL round-bottom flask under the column, and elute the pyriproxyfen residues with 55 mL of hexane-ethyl acetate (4 1, v/v). Evaporate the eluate by rotary evaporation under reduced pressure in a <40 °C water-bath and reconstitute the sample in 2.0 mL of toluene with sonication for analysis (Section 6.2). 

This procedure was compared with sequential extractive techniques employing alkaline hydrolysis of dried plant tissue followed by extraction of the acidified mixture with ethyl acetate. Fractions were individually evaluated for phytotoxic properties. Selected fractions from those showing a positive response were analyzed by gas-liquid chromatography. Structural identification and characterization of the individual components in these selected fractions were accomplished by gas chromatography-mass spectrometry. 

By adding one equivalent of alcohol to CDI at room temperature with or without base it is possible to isolate the imidazole-iV-carboxylate, which then reacts with a second mole of ROH to yield the carbonate. As in the case of alcoholysis of imidazolides, the reaction can be accelerated so effectively with catalytic amounts of NaOC2H5 or ImNa that it takes place in most cases exothermically, even at room temperature. However, tert-butyl alcohol, even when in excess, affords with CDI and base catalysis at room temperature only the imidazole-N-tert-butylcarboxylate, obviously for steric reasons. At higher temperature the carbonic ester is formed. Mixed carbonates such as ethyl benzyl carbonate or ethyl terf-butyl carbonate can be prepared with two different alcohols added sequentially.C9],[229]... 

O-acetylophiocarpine (381) with ethyl chloroformate afforded the C-8—N cleaved urethane 382 in quantitative yield. Sequential treatment of 382 with silver nitrate, PCC, sodium hydroxide, and p-toluenesulfonic acid in ethanol furnished acetal 384, which was reduced with lithium aluminum hydride followed by hydrolysis to afford the hemiacetal 385. Oxidation of 385 with PCC provided (+ )-a-hydrastine (369). Similar treatment of O-acetylepi-ophiocarpine (386) afforded ( )-/J-hydrastine (368) however, in this case, C—N bond cleavage of 386 with ethyl chloroformate proceeded without regioselectivity. 

Although the metathesis of ene-ynes is a valuable method for the preparation of 1,3-butadienes, and may be used for Diels-Alder reactions, a problem arises from the need to employ either a high temperature or a Lewis add to accelerate the cycloaddition, which is usually not feasible with the Grubbs catalyst Therefore, the combination of metathesis and cycloaddition is usually performed in sequential fashion (as just shown, and highlighted earlier) [264]. However, Laschat and coworkers [265] have shown the Lewis acid BC13 to be compatible with the Grubbs I catalyst (6/3-13). Reaction of 6/3-92 and ethyl acrylate using a mixture of 2.5 equiv. of the Lewis acid and 10 mol% of 6/3-13 led to 6/3-93 in 60% yield (Scheme 6/3.27). 

The preparation of malonic acid monoesters has been demonstrated using the microbial nitrilase activity of Corynebacterium nitrilophilus ATCC 21 419, Gordona terrae MA-1, or Rhodococcus rhodochrous ATCC 33 025 to hydrolyze methyl cyanoacetate, ethyl cyanoace-tate, M-propyl cyanoacetate, isopropyl cyanoacetate, M-butyl cyanoacetate, tertbutyl cyanoacetate, 2-ethylhexyl cyanoacetate, allyl cyanoacetate, and benzyl cyanoacetate [96]. By maintaining the concentration of nitrile in a reaction mixture at <5 wt%, significant inactivation of the nitrilase activity was avoided for example, a total of 25 g of M-propyl cyanoacetate was added in sequential 5g portions to a lOOmL suspension of Rhodococcus rhodochrous ATCC 33 025 cells (OD630 = 5.6) in 50 mM phosphate buffer (pH 7.0) over 30h at 25 °C to produce mono-M-propyl malonate in 100% yield (Figure 8.17). 

IR absorption spectra were superimposable onto those of the physical mixtures of the respective homopolymers. The molar ratio of the poly(MMA) and polyethylene blocks, however, decreased as the Mn of the prepolymer increased, especially when it exceeded ca. 12 000 at which polyethylene began precipitating as fine colorless particles. It is noteworthy that smooth block copolymerization of ethyl acrylate or methyl acrylate to the growing polyethylene chain (Mn = 6 600-24 800) can be realized by the sequential addition of the two monomers. 

An equimolar (10 mmol) mixture of benzoyl chloride and n-butyl oxide adsorbed on 5 g graphite A was sequentially irradiated with 90 W incident power. The conversion reached 80% (Yield of isolated n-butyl benzoate (69) 62%). With ethyl oxide, the yield of ethyl benzoate (68) was lower, but noteworthy considering the volatility of this oxide, and the significant retentive power of graphite towards organic compounds. These preliminary results have not yet been expanded, but it is certain that more reactive ethers, like those substituted with sec- or teri-alkyl, benzylic or allylic groups, are deavable in the same way. 

Petrillo reported that the bis-acetoxymethylpyrrole 83 undergoes a sequential Diels-Alder reaction of the in situ generated 2,3-dimethylpyrrole with carbodienophiles (such as maleic anhydride, maleimide, ethyl maleate, fumaronitrile, and ethyl acrylate) to afford the octahydrocarbazoles 84 which can be oxidized with DDQ to the corresponding carbazole derivatives . 

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