L-Phenylprop

An acyclic enone, 2-ethyl-l-phenylprop-2-en-l-one, was reduced with the yeast Pichia stipitis CCT 2617 [19cj. The reduction proceeded chemo- and enantioselec-tively to afford (S)-2-ethyl-l-phenylprop-2-en-l-ol (65% yield, >99% ee). XAD-7 was used to decrease and control the concentration of both the substrate and the product (Figure 8.25). 

A number of biotransformations have been accomplished by rhodococci, including, for example, the hydrolysis of nitriles including polyacronitriles (Tauber et al. 2000), and the reduction of the conjugated C=C double bond in 2-nitro-l-phenylprop-l-ene (Sakai et al. 1985). 

The enantiomeric reduction of 2-nitro-l-phenylprop-l-ene has been studied in a range of Gram-positive organisms including strains of Rhodococcus rhodochrous (Sakai et al. 1985). The enantiomeric purity of the product depended on the strain used, the length of cultivation, and the maintenance of a low pH that is consistent with the later results of Meah and Massey (2000). It has been shown that an NADPH-linked reduction of a,p-unsaturated nitro compounds may also be accomplished by old yellow enzyme via the flcf-nitro form (Meah and Massey 2000). This is formally analogous to the reduction and dismutation of cyclic enones by the same enzyme (Vaz et al. 1995), and the reductive fission of nitrate esters by an enzyme homologous to the old yellow enzyme from Saccharomyces cerevisiae (Snape et al. 1997). 

In a related study, Rieke and Guijarro studied the configurational stability of the zinc-carbon bond in 2-butylzinc bromide and (l-phenylprop-2-yl)zinc bromide, using a bis(oxazoline) as a chiral resolving agent.72 From their data, the authors determined the A 6 of inversion at the secondary carbon of (l-phenylprop-2-yl)zinc bromide to be 113.8 kj mol-1. 

Several Sonogashira adducts of heteroaromatics including some pyridines (see Section 4.3) and pyrimidines underwent an unexpected isomerization [69]. This observed isomerization appeared to be idiosyncratic, and substrate-dependent. The normal Sonogashira adduct 100 was obtained when 2-methylthio-5-iodo-6-methylpyrimidine (99) was reacted with but-3-yn-ol, whereas chalcone 101, derived from isomerization of the normal Sonogashira adduct, was the major product when the reaction was carried out with l-phenylprop-2-yn-l-ol. 

The high concentration of ammonia that is required for selective formation of primary allylic amines suggests that ammonia is much less reactive toward nucleophilic attack on an allyl ligand than the primary allylic amine products. The reactivity of different nucleophiles toward allyl ligands was assessed by treating the allylir-idium complex 6a with ammonia and l-phenylprop-2-en-l-amine. No product from allylation of ammonia was detected from this reaction. In addition, the reaction of an allylic carbonate with the combination of ammonia and l-phenylprop-2-en-l-amine in the presence of lb did not produce detectable amounts of the product from allylation of ammonia. These results confirm that the primary amine is much more... 

The reaction of phenyl-substituted alkenes (2-phenylprop-l-ene, ( )-l-phenylprop-l-ene, 1,1-diphenylethene, 1,1-diphenylprop-l-ene) with F-Teda BF4 (6) in the presence of various alcohols results in the formation of vicinal fluoro alkoxy adducts with Markovnikov-type regioselec-tivity.89,94 The stereochemistry of the fluorination-methoxylation addition reaction is slightly syn predominant in the case of (Z)-stilbene, indene, and dibenzosuberenone, while equal amounts of both diastereoisomers are formed in the case of ( )-l-phenylprop-l-ene and acenaphthylene. 

Photochemical reactions of alkynic ketones, e.g. l-phenylprop-2-yn-l-one (111) in alcohols gave 2,5-disubstituted furans, postulated as arising from a 1 1 adduct whose... 

The protected malondialdehyde (320) reacts with diethyl malonate to give the substituted malonic ester, so providing access to ethyl 2-oxopyran-3-carboxylate (63JOC1443). The corresponding 6-phenyl derivative results from the reaction of 3-methoxy-l-phenylprop-2-en-l-one with malonate carbanion (64RTC31). 

Hydration of alkynes yields carbonyl compounds and the ketone used in pyrylium syntheses has been successfully replaced by an alkyne (65CB334). Phenylacetylene, for example, reacts with 3-chloro-l-phenylprop-2-en-l-one to yield the 2,6-diphenylpyrylium salt. 

Dehydrobromination of 2,3-dibromo-l,l,l-trifluoro-3-phenylpropane (30) and 2-bromo-3,3,3-trifluoro-l-phenylprop-l-ene (31) leads to 3,3,3-trifluoro-1-phenylprop-1-yne (32).62... 

Propargylic alcohols bearing a terminal triple bond react with electron-rich aromatic compounds in the presence of thiolate-bridged diruthenium complexes to give the propargylated aromatic compounds.30 l-Phenylprop-2-yn-l-ol, for example, reacts with 2-methylfuran to form (15). Intramolecular examples of the reaction were also reported. The process is believed to involve electrophilic attack by the ruthenium-stabilized propargyl cation. 

Radical substitution reactions involving allylic tin derivatives could be accompanied by a photoinduced 1,3-rearrangement54,55. A photostationary mixture of cinnamyl(tri-phenyl)stannane with its regioisomer l-phenylprop-2-enyl(triphenyl)stannane has been shown to form in the photolysis of ( )-cinnamyl(triphenyl)stannane in benzene under aerobic conditions, or in the presence of halogenated organic compounds or radicaltrapping reagents (equation 21). 

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