Jeffrey conditions

Comins et al. [70] showed that V-acetyl-2,3-dihydro-4-pyridone reacts in a regio- and stereoselective manner to give the 5-exo-cyclization products. Product 80 is obtained under Jeffrey conditions, whereas hydride capture delivers the formal 1,4-addition product 81 (Scheme 6.22). 

Scheme 19.8 Preparation of poly-3-alkylthiophenes from 2-halo-3-alkylthiophenes using Jeffrey conditions.

An interesting set of conditions are the Jeffrey conditions, using a polar solvent and a quaternary ammonium salt (Table 5.1). Detailed investigations have shown that the correct choice of ammonium salt and addition of a small amount of water can be critical. Under the right conditions, many Heck reactions can mn at or near room temperature. The main effect is due to the cation of the phase-transfer catalyst, not the anion, and the effect was most marked when inorganic bases were used. The phase-transfer catalyst may facilitate the final step of the Heck mechanism. 

Not many operating data of large-scale hquid/hquid reactions are published. One study was made of the hydrolysis of fats with water at 230 to 260°C (446 to 500°F) and 41 to 48 atm (600 to 705 psi) in a continuous commercial spray tower. A small amount of water dissolved in the fat and reacted to form an acid and glycerine. Then most of the glycerine migrated to the water phase. Tlie tower was operated at about 18 percent of flooding, at which condition the HETS was found to be about 9 m (30 ft) compared with an expec ted 6 m (20 ft) for purely physical extrac tion (Jeffreys, Jenson, and Miles, Trans. In.st. Chem. Eng., 39, 389-396 [1961]). A similar mathematical treatment of a batch hydrolysis is made by Jenson and Jeffreys (In.st. Chem. Engrs. Symp. Ser, No. 23 [1967]). 

This topic has a long history of research (Harrison and Aiyer, 1920 Sturgis, 1936 Pearsall and Mortimer, 1939 Shioiri, 1943 De Gee, 1950 Takai, 1952 Ponnamperuma, 1955 Baas-Becking et al., 1960 Jeffrey, 1961 Patrick, 1966 Ponnamperuma, 1972 Yu, 1985 Kyuma, 2003). The following factors result in conditions differing from those in simple aquatic systems ... 

California black oak and white fir and less often on incense cedar in the San Bernardino Mountains. No direct effects of oxidants have been noted on the mistletoe plant itself under field conditions. The true mistletoe obtains mainly water from its host and would be indirectly affected by debilitation of die host tree. The dwarf mistletoes Arceuthobium spp.) are common on ponderosa, Jeffry, and sugar pines in the San Bernardino National Forest. They depend on their host for both water and carbohydrates. Heavily infected or broomed" branches on ponderosa or Jeffrey pines severely injured by ozone often have more annual needle whorls retained than do uninfected branches on the remainder of the tree. The needles are also greener. It can be hypothesized that the infected branch is a carbohydrate sink where a pooling of carbohydrates occurs higher carbohydrate concentrations may be instrumental in either preventing or helping to repair ozone injury to needles on the broomed branches. In the long term, stresses from mistletoe and ozone are probably additive and hasten tree death. 

Another group of compounds well suited for CSIA because of their widespread occurrence are plant pigments (Bidigare et al., 1991 Kennicutt et al., 1992). Chorophylls and carotenoids are involved in photoautotrophic reactions that produce organic matter and can provide information on the nutritional and light conditions of algae (Welschmeyer and Lorenzen, 1985 Jeffrey et al., 1997). In fact, recent work has shown that a 5.1%o... 

A discussion of the traction boundary conditions—where the totaJ normal stress is prescribed on the inflow and outflow boundaries—for Jeffreys-type fluids is given in [31], and for Maxwell-type fluids in [32]. 

We first consider Jeffreys-type models, namely system (7) with e < 1, which is complemented with the Dirichlet boundary condition... 

M. Renardy, Existence of steady flows of viscoelaistic fluids of Jeffreys-type with traction boundary conditions, Diff. Int. Eq., 2 (1989) 431-437. 

Any model linear in its location parameters 0 has a uniform Jeffreys prior p 6i) over the permitted range of 0 . This condition occurred in Examples 5.6 and 5.8, where the model = p + eu with location parameter p was used. The Jeffreys prior p(0 ) is likewise uniform for any model nonlinear in 0 , over the useful range of its linearized Taylor expansion that we provide in Chapters 6 and 7. 

A variety of hybridization conditions have been described for different fingerprinting probes (Jeffreys et at, 1985a, b Chen et al, 1990 Vassart et al, 1987). The method of Church and Gilbert (1984) is particularly useful due to the simplicity of the hybridization solution. 

Equations 12.45103 and 12.46104 show two examples of intramolecular Heck olefination. In the first case, under Jeffrey s ligandless conditions, the Pd catalyst also acts to isomerize a C=C bond to give a final product that has the C=N bond in conjugation with the aromatic ring. The second example demonstrates how the Heck reaction can cause alkynes as well as alkenes to undergo 1,2-insertion. The transformation is also a nice application of tandem Pd-catalyzed reactions to create a rather complex ring system. 

Rawal applied the Heck cyclization in elegant fashion to the construction of indole alkaloids. His route to geissoschizine alkaloids features a novel ring D formation, 294 to 295-296 [287]. Whereas classical Heck conditions favor the isogeissoschizal (296) product, the ligand-free modification of Jeffrey favors the geissoschizal (295) stereochemistry. 

In 1926-27, Jeffreys (J3, J4) attempted to extend Rayleigh s result to a more realistic set of boundary conditions, first using finite differences to obtain successive approximations to the solution of Eq. (31) and later using a method of undetermined coefficients for the case corresponding to two solid conducting boundaries. In the latter manner, he computed a critical Rayleigh number of 1709.5. 

---