With tetrapropylammonium

Benzene p-dialdehyde (terephthalic aldehyde) produces the anion-radical at the potential of the limiting current of its first reduction wave in DMSO with tetrapropylammonium salt as a supporting electrolyte. The anion-radicals demonstrate two ESR spectra. One of them is superimposed... 

Hydroboration occurred from the less hindered top face of rac-29 and resulted in the formation of alcohol rac-30. After a three-step sequence which included oxidation with tetrapropylammonium perruthenate (TPAP), methyl lithium addition and repeated oxidation with TPAP, ketone rac-31 was isolated. Finally, epimerization of the stereogenic center at C-7 to the correct configuration and methylenation with the Lombardo reagent led to the formation of racemic kelsoene (rac-1). 

Reductive alkylation of -caprolactone (1 equiv) with a 2 0.25 mixture of Grignard reagent and Zn(BH4)2 affords monoalkylated diols, which can be further selectively oxidized with tetrapropylammonium perruthenate (TPAP) into the expected monoalkylated lactones <2002CR571>. 

Most compounds of this type are derived from methyl hexosides methyl 2,6 3,4-dianhydro-a-D-altropyranoside309 398 400 516 and methyl 2,5 3,6-dianhydro-a- and /J-n-mannol iiranosides.517 From hexuloses, the synthetically useful l,5 3,6-dianhydro-D-<2raZ)i o-hex-2-ulose (172) has been prepared by regioselective monobenzylation of l,5 3,6-dianhydro-D-mannitol at C-4 (171a — 171b) followed by oxidation with tetrapropylammonium perruthenate.518... 

The second example involves straightforward doping of methyl modified silica, denoted as ormosil, with tetrapropylammonium perruthenate via the sol-gel process [102] (Table 3). A serious disadvantage of this system are the low TOFs of 1.0 and 1.8 h 1 observed for a primary aliphatic alcohol and allylic alcohol, respectively. 

Some of the samples were synthesized ithout A190 . The syntheses with tetrapropylammonium iodide (TPA J ) as template were carried out with a varying Si09/Al90 ratio in the range 25 - 400. The batch composition of the template-free synthesis was... 

When 125 was subjected to a two-step sequence, reductive cleavage of the 0-0 bond and subsequent oxidative dehydration, by treatment with zinc in AcOH, the allylic diol 135 and the 1,2-oxazocine 126, as minor product, were isolated. Oxidation of the diol 135 under several different reaction conditions (pyridinium chlorochromate (PCC), 2-iodoxybenzoic acid (IBX)/EtOH, IBX/DMSO, Pyr/SOj) gave 126 in high yield (68-92%), while with tetrapropylammonium perruthenate/Wmethylmorphaline Ar-oxidc (TPAP/NMO) as oxidizing agent 126 was the minor product and the a,/3-unsaturated 7-butyrolactone 136 was obtained in 68% yield (Scheme 28) <2005JOC6995>. 

Chiral nitrosoureas can be easily prepared starting from disubstituted pyrrolidines possessing C2 symmetry. Thus (27 , 57 l-dimcthyI pyrrolidine can be smoothly converted, by reaction with phenoxyhydroxamic acid in pyridine solution to the corresponding (V-hydroxyurea 1. Oxidation of 1 with tetrapropylammonium periodate in dichloromethane gives the short-lived nitroso dienophile 2 which reacts with 1,3-cyclohexadiene to give the bicyclic 3,6-dihydro-2//-1,2-ox-azine 3 in 81% yield and d.r. 99 1, The absolute configuration of the reaction product was ascertained unequivocally by synthetic methods as (17 ,45)107. 

Following another synthetic pathway, an intramolecular cycloaddition was carried out by treating the JV-acylhydroxylamine 5 a with tetrapropylammonium periodate in chloroform. Under these conditions intramolecular [4 + 2] cycloaddition occurs with complete simple diastereoselectivity to give the corresponding bicyclic dihydro-1,2-oxazine cis-6a as the sole product118-121. However, when the IV-acyl hydroxy larnine bears a substitutent R1 the stereocontrol is incomplete. 

Recently, Kibayashi s group (85JA5534) elegantly carried out the stereo-controlled total synthesis of gephyrotoxin (skin extracts of neopropical poison dart frog) based upon an intramolecular nitroso Diels-Alder reaction. The hydroxamic acid 365 was treated with tetrapropylammonium periodate... 

MCM-41, synthesized using hexadecyltrimethylammonium hydroxide, was ion-exchanged with tetrapropylammonium hydroxidc-MCM-41 by shaking a suspension of 2.00 g of MCM-41 in 1.22 g of 25.0 wt. % of tetrapropylammonium hydroxide solution in 1 L at room temperature overnight. The solid was recovered by centrifugation, washed in water and subjected to a hydrothermal treatment at 170°C in a 15-mL Teflon autoclave. The recrystallized MCM-41 was recovered by centrifugation, washed with deionized water and dried under vacuum at 60 °C. The template was removed by calcination in a stream of air al 500 °C for 6 h [91]. 

Oxidation of diene-containing hydroxamic acids has been reported to give acylnitroso species which undergo spontaneous hetero-IMDA reactions to give heterobicyclic ketones. (E,E)-N-Hydroxy-5,7-dodecadienamide, upon treatment with tetrapropylammonium periodate, gave the pyrido[l,2-b][l,2]oxazine structure in high yield88. 

Figure 7. Large crystals of silicalite-I that were synthesized alkaline-free with tetrapropylammonium bromide as template. (Reproduced with permission from reference 46. Copyright 1990.)...

Let us take one example to try to visualize more precisely the above discussion. The details of a part of the XRD pattern are shown in fig. 3 for the as synthesized (SYN with tetrapropylammonium template), hydrated (WAT) and four xylene molecules adsorbed per unit-cell (XYL-1) of B-ZSM-5 sample from ref. 35 and 36. The calcined form exhibits a monoclinic structure (P2l/n space group) whereas SYN and WAT forms correspond to orthorhombic phases (Pnma space group). The striking differences in XRD patterns are seen in fig. 3. The p-xylene adsorption is known (27) to take place in two steps. The first one, up to four molecules per u.c. and designated XLY-I, corresponds to the formation of a low coverage complex and the second one (XYL-II) to a maximum of xylene adsorption with 8 molecules per u.c. The location of p-xylene could even be determined in the ZSM-5 channel by careful analysis of powder X-ray diffraction patterns using the trail error method (35) as shown in fig. 4. 

C.iii. Nitroso-Type Compounds. Nitroso compounds (R—N=0) show reactivity as dienophiles in Diels-Alder reactions, giving heterocyclic rings. In Kibayashi s synthesis of fasicularin, " for example, hydroxamic acid 180 was treated with tetrapropylammonium periodate in the presence of 9,10-dimethyl-anthracene to give transient acylnitroso compound 181, and the resultant Diels Alder product 182 was formed in 84% yield. In this particular example, the Diels-Alder adduct essentially "protected" the acyl nitroso unit, which was used in a subsequent reaction. 

Two further separation techniques have been described for the resolution of the oestranes reversed phase ion-pair partition (Hermansson, 1978) and argentation reversed phase HPLC (Tscheme and Capitano, 1977). In the former technique C2 or Cg columns were coated with 1-pentanol and used with tetrapropylammonium hydroxide as an ion-pairing reagent. In the latter technique an ODS stationary phase was used with a mobile phase of methanol-5% silver nitrate (60 40) to elute oestriol, equilin, oestrone and oestradiol. 

The high-resolution characterization of the various rectorite samples was performed at 200 and 400 Kv in a Jeol-2000 electron microscope. The analytical microscopy was performed in a Jeol-lOOCX machine fitted with a Tracor Northern 5500 x-ray detector. Samples were embedded in resin (6, 7) and microtomed in the direction perpendicular to the basal planes (8). The parent rectorite was intercalated with tetrapropylammonium bromide solutions (TPA-Br) to improve the clay stability in the microscope column. The pillared rectorite was instead dispersed in isopropyl alcohol the clay particles were then separated by ultrasonification and deposited onto copper grids. 

Variants of NaAOT have been prepared and examined by various authors [127, 128]. Two strategies are important replacement of the counterion and that of the chain. The former has been carried out in a variety of systems used in particle synthesis (see Section 2.4.2 and Chapter 5), but generally the question of water solubilization was not addressed directly. Eastoe et al [127], for example, showed that with tetrapropylammonium ion, (C3H7)4N replacing Na in NaAOT, cylindrical instead of droplet micelles can form at a w value of 10 or even less. Incorporation of NH/, however, yielded only spherical micelles. The maximum values of w at 25 C for the above three varieties of AOT were 12.0 for Na (AOT)", 12.0 for (NH4) (AOT) and 22.0 for The value increased perceptibly in case of sodium, but... 

The oxidation of alcohols with (l,l-dimethylethyl)benzene-sulfenamide is extremely mild and many sensitive functional groups such as epoxides and alkenes are tolerated hy the reaction conditions (eq 5). In the case of alcohol 1, oxidation with tetrapropylammonium perruthenate (TPAP) resulted in only 58% yield and Swern oxidation was unsuccessful. Epimerizable aldehydes such as the protected phenylglycinol 2 do not undergo racemization when oxidized (eq 6). ... 

The kinetic data in Table 1 demonstrates that S-4 anchimeric assistance is not important in the hydrolysis of acyclic alkyl chlorides [e.g., n-hexyl chloride solvolyzes 1.8 times faster than PhS(CH2)3Cl in 20 mole % aqueous dioxane at 100°C ]. Some data on cyclic systems will be presented here to demonstrate that proximity effects can drastically affect S-4 participation. The formation of (35) and (36) from treatment of 3j -methanesul-fonyloxy-5-a-methylthiocholestane (34) with tetrapropylammonium acetate was rationalized in terms of S-4 participation as shown. Ireland and Smith found that the rates of solvolysis of (37) and (38) were slower [/Crei(77°C) = 0.46 and 0.21, respectively] than the rate for trans-4-t-huty ... 

The THP protective group was removed with NH4CI in refluxing methanol (24), The 1,4-diol 25 was oxidized directly to the lactone 21 with tetrapropylammonium pemithinate (TPAP) and 4-methylmorpholine-N-oxide as co-oxidant in CH2CI2 (25),... 

In the solid state, lb afforded planar [1 + l]-type pentacoordinated Cl /Br complexes by using pyrrole NH, bridging CH, and aryl ortho-CH units (Fignre 4.3a). Planar lb Cl /Br anions stacked along with tetrapropylammonium cations (TPA+) to form charge-by-charge columnar strnctnres with distances between the halides of 8.54 and 8.67 A for Ck and Br, respectively, and those between the receptor-halide complexes of 7.29 and 7.44 A, respectively. Similarly, (J-substituted 2b and 3b exhibited the formation of [1 + l]-type complexes. 

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