Phenyl groups, adding

When benzaldehyde or its substituted derivatives are added to carbon disulfide and a-aminonitrile, the corresponding 2-mercapto-5-(p-R-benzylideneamino)thiazoles (215), R = hydrogen atom or a propenyl or phenyl group and Ar = aryl, are obtained (Scheme 112) (393, 442, 694). Yields ranged from 40 to 60% (Table II-34b). 

The rate constants for benzoyloxy and phenyl radicals adding to monomer are high (> KF M-1 s for S at 60 CC - Table 3.7). In these circumstances primary radical termination should have little importance under normal polymerization conditions. Some kinetic studies indicating substantial primary radical termination during S polymerization may need to be re-evaluated in this light.161 Secondary benzoate end groups in PS with BPO initiator may arise by head addition or transfer to initiator (Section 8.2.1). 

However, none of these compounds can be easily resolved except TM (16) Itself. Me prefer to resolve as early as possible, (page T 94), so It is better to carry out the Diels-Alder reaction with acrylic acid and resolve acid (19) before adding the phenyl group by a Grignard reaction. The benzylic alcohol group in (20) can be taken out by metal-anunonia reduction. Syrithesis ... 

Polysilanes containing phenyl groups are thermally stable up to 350°C while methylmethoxypoly-silanes without phenyl groups decompose at 250 - 300°C. When methylmethoxyphenylpolysilanes are heated to 350°C methylmethoxysilanes distil off and a polymer is formed which is nearly free of methoxy groups. In contrast to the thermal reaction of polydimethylsilanes no polycarbosilane structures can be observed even if polyborodiphenylsiloxane is added as catalyst (Figure 3.). 

Replacement of the hydroxyl group on the phenyl ring with a carboxyl group forms a molecule of benzoic acid. Addition of a hydroxyl at the 2-position on a benzoic acid molecule forms 2-hydroxybenzoic acid or salicylic acid. The slightly more complex phenylpropanoid skeleton contains a linear three-carbon chain (the propanoic group) added to the benzene ring (the phenyl group). Addition of ammonia to carbon 2 of this three-carbon side chain yields the amino acid phenylalanine (Fig. 3.3). Phenylalanine... 

Interesting results concerning phenyl group participation were observed with ( )-styryl(phenyl)iodonium tetrafluoroborate (26) using a deuterated substrate (eq 12)16 When 26-ad was heated in trifluoroethanol (TFE) at 60 °C, slow reaction gave die E isomer of substitution product 28 quantitatively, but the deuterium was completely scrambled between the a and p positions. This strongly indicates that a symmetrical intermediate is involved during the reaction and the most reasonable one is vinylenebenzenium ion (27) formed by phenyl participation. This intermediate also explain the exclusive formation of the retained ( )-28. 

The use of cyclic alkenes as substrates or the preparation of cyclic structures in the Heck reaction allows an asymmetric variation of the Heck reaction. An example of an intermolecular process is the addition of arenes to 1,2-dihydro furan using BINAP as the ligand, reported by Hayashi [23], Since the addition of palladium-aryl occurs in a syn fashion to a cyclic compound, the 13-hydride elimination cannot take place at the carbon that carries the phenyl group just added (carbon 1), and therefore it takes place at the carbon atom at the other side of palladium (carbon 3). The normal Heck products would not be chiral because an alkene is formed at the position where the aryl group is added. A side-reaction that occurs is the isomerisation of the alkene. Figure 13.20 illustrates this, omitting catalyst details and isomerisation products. 

Substituted cyclohexanones, bearing a methyl, isopropyl, tert-butyl or phenyl group, give, on deprotonation with various chiral lithium amides in the presence of chlorotrimethylsilane (internal quench), the corresponding chiral enol ethers with moderate to apparently high enantioselec-tivity and in good yield (see Table 2)13,14,24> 29 36,37,55. Similar enantioselectivities are obtained with the external quench " technique when deprotonation is carried out in the presence of added lithium chloride (see Table 2, entries 5, 10, and 30)593. 

Treatment of /3,-y-unsaturated acids with iodine in sodium bicarbonate solution may give y-iodo-/3-lactones in good yield (equation 94), but if potassium iodide is added then /3-iodo-y-lactones are produced. One compound, 4-phenyl-3-butenoic acid, gave the y-lactone even when KI was not present, presumably due to the phenyl group favoring development of carbonium ion character at C-4 in the intermediate iodine complex. With... 

If the substituent on the nitrogen atom of an amide is a phenyl group, the ending -amide is changed to -anilide. Cyclic amides are known as lactams, and the lUPAC names are derived by adding the term lactam at the end of the name of the parent carboxylic acid. 

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