Extended reaction conditions

With Lewis acidic reagents (TMSI or BBr3) under extended reaction conditions, two benzyl groups remained. Forcing hydrogenolysis resulted in reduction of the C-14 carbonyl group. 

Table VIII shows the structure of the substrates that have been used in comparative studies by the New Hampshire group. Some of these substrates are quite hindered, but, with the NMDPP, CAMPHOS, DIOP, and ACMP catalysts, quantitative yields are usually obtained under the extended reaction conditions described above.10 The MDPP catalyst does not give a good yield in most instances even under extended conditions.

The extended reaction conditions involve higher pressure and temperature than are normally used for Wilkinson-type catalysts and unhindered substrates. 

TIP In equilibrium reactions examine the stability of the products. If the desired product is thermodynamically favored, extend reaction conditions. Yields may be raised by crystallizing the product from the reaction. 

With some ligands, further oxidation to the W(V) ions occur under extended reaction conditions. 

This reaction can be extended to unsaturated nitriles, eg, acrylonitrile, which can give trihalostannyl-functional carboxyHc acids, esters, and amides by the proper choice of solvents and reaction conditions (156). 

Stereoregular Polymerization. Chemists at GAF Corporation were first to suggest that stereoregularity or the lack thereof is responsible for both nontacky and crystalline or tacky and amorphous polymers generated from IBVE with BF2 0(C2H )2, depending on the reaction conditions (22,23). In addition, it was shown that the crystalline polymer is actually isotactic (24). Subsequentiy, the reaction conditions necessary to form such polymers have not only been demonstrated, but the stereoregular polymerization has been extended to other monomers, such as methyl vinyl ether (25,26). 

Reagent grade potassium cyanide was purchased from Matheson, Coleman and Bell, and dried at IIB C (0.5 itm) for 24 hr. The checkers found it necessary to use newly purchased potassium cyanide. The use of potassium cyanide which was several years old gave incomplete reaction even at extended reaction times. The large excess of potassium cyanide is used simply to obtain convenient reaction times. For comparison, use of 1.5 equiv of KCN gave 38% conversion under conditions where 3 equiv produced 100% conversion. 

Nitronium fluorosulfate in fluorosulfonic acid adds electrophilically across the double bond offluoroolefins in a nonspecific manner. Tnfluorochloroethylene reacts accordingly with nitronium fluorosulfate to give a 2.1 mixture of regio-isomers [7] (equation 7). Under these reaction conditions perfluoropropylene is unreactive even after extended heating at 80 C 2-Nitroperfluoropropyl fluorosulfate is obtained on treatment of the perfluoropropylene with nitronium fluorosulfate in antimony pentafluoride [5] (equation 8). 

It has been shown that acetamidothiophenes 22 can be converted to either chlorothieno[2,3-h]pyridines 23 or chlorothieno[2,3-h]pyridinecarboxaldehydes 24 using POCI3 and DMF by appropriate choice of reaction conditions. However, unlike the acetanilides, initial ring formylation rather than side-chain formylation is believed to lead to the formation of the pyridine ring. These reactions have been extended to the synthesis of the isomeric thieno[3,2-I>]- and thieno[3,4-I>]pyridines, 25 and 26, from 3-acetamidothiophene and 3-acetamido-2,5-dimethylthiophene, respectively. 

Baer and Ryan (Bl) have extended the calculations of Hicks and Frazer by analyzing the effect of the activation energy on the time required to achieve runaway reaction conditions. Their calculations demonstrated that the slope on a plot of log(r)1/2 versus log Q is related to the activation energy of the propellant-heating reaction by the expression... 

Kinetic studies using 1,9-decadiene and 1,5-hexadiene in comparison widi catalyst 14 and catalyst 12 demonstrate an order-of-magnitude difference in their rates of polymerization, widi 14 being the faster of the two.12 Furdier, this study shows diat different products are produced when die two catalysts are reacted widi 1,5-hexadiene. Catalyst 14 generates principally lineal" polymer with the small amount of cyclics normally observed in step condensation chemistry, while 12 produces only small amounts of linear oligomers widi die major product being cyclics such as 1,5-cyclooctadiene.12 Catalyst 12, a late transition metal benzylidene (carbene), has vastly different steric and electronic factors compared to catalyst 14, an early transition metal alkylidene. Since die results were observed after extended reaction time periods and no catalyst quenching or kinetic product isolation was performed, this anomaly is attributed to mechanistic differences between diese two catalysts under identical reaction conditions. 

Subsequently, the scope of the reaction was extended to N-nucleophiles 82. Because the inherent basicity of the substitution products 83 imposed some problems concerning catalyst decomposition, the addition of catalytic amoimts of piperidine hydrochloride (pip-HCl) proved to be necessary. Under optimized reaction conditions different aromatic amines 82 were allylated with almost exclusive regioselectivites in favor of the ipso substitution products 83 (eq. 1 in Scheme 20) [64]. 

To verify that steady state catalytic activity had been achieved, the catalyst was allowed to operate uninterrupted for approximately 8 hours. The catalyst was then removed from the reactor and the surface investigated by XPS. The results are shown in Figure 2c. The two major changes in the XPS spectrun were a shift in the iron 2p line to 706.9 eV and a new carbon Is line centered at 283.3 eV. This combination of iron and carbon lines indicates the formation of an iron carbide phase within the XPS sampling volume.(J) In fact after extended operation, XRD of the iron sample indicated that the bulk had been converted to FecC2 commonly referred to as the Hagg carbide.(2) It appears that the bulk and surface are fully carbided under differential reaction conditions. 

We have shown that the direct arylation of acrolein toward the synthesis of cinnamaldehyde derivatives was an efficient procedure. Using the palladacycle 1 as catalyst, substituted aldehydes 3 were prepared with up to 87% isolated yield from condensed aiyl bromides (Scheme 21.1, Route 1) that was extended successfully to heteroaiyl bromides, like bromoquinolines (6). Alternatively, the acrolein diethyl acetal was used as olefin and a selective formation of the saturated ester 4 was attained under the same reaction conditions (Scheme 21.1, Route 2). The expected aldehydes 3 were, however, obtained from most of the aiyl halides used under modified conditions. It was shown that the addition of n-Bu4NOAc in the medium... 

In addition to bromides and iodides, the reaction has been successfully extended to chlorides,163 triflates,164 and nonafluorobutanesulfonates (nonaflates).165 These reaction conditions permit substitution in both electron-poor and electron-rich aryl systems by a variety of nitrogen nucleophiles, including alkyl or aryl amines and heterocycles. These reactions proceed via a catalytic cycle involving Pd(0) and Pd(II) intermediates. 

Thus far, we have discovered and demonstrated a new and effident method for the synthesis of indoles from various carbonyl compounds. This, in conjunction with the use of alkyries in the palladium-catalyzed indolization, widens the spectrum of indoles that can be prepared by these means. The simple procedure, mild reaction conditions, and ready availability of the starting materials render these methods valuable additions to indole chemistry. We next extended this method to the synthesis of the indole core of a PGD2 receptor antagonist, laropiprant 3. 

B (12.10) Under various reaction conditions, the isomer ratio of A was consistently higher than B. Isomer A is the expected regioisomer if the diene and dienophile react in their preferred orientation within a mixed micelle in which the quaternary ammonium groups are at the aggregate-water interface and the rest of the molecule is extended into the micelle interior (Figure 12.2). Isomer B comes about from the misalignment of the diene and dienophile within the mixed micelles. 

Catalytic hydrogenolysis of the bisbenzylated Boc-neonactin A (21 in Scheme 4.97) using 10% Pd/C provided an inseparable mixture of the deben-zylated product and the N4-deshydroxy compound (22).343 Various manipulations of the reaction conditions including changing the solvent, the mol equivalents of Pd, and the reaction time proved unsuccessful. But with the use of an extended period of reaction time, the N-O bond can be completely removed. The bisbenzylated Boc-neonactin A and 10% Pd/C in EtOH were stirred under a hydrogen atmosphere for 7 days, providing the N4-deshydroxy compound in 70% yield (Scheme 4.97). 

The summations extend from n = 2 to n. = oo.) Keii [Kinetics of Ziegler-Natta Polymerization, Kodansha, Tokyo, 1972] has noted that under steady-state reaction conditions, the number of polymer molecules with degree of polymerization n desorbing per unit catalyst surface area in unit time may be written as... 

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