L-Phenyl-3-buten

What product would you expect from the reaction of l-phenyl-2-butene with NBS Explain. 

For unsymmetrical allylic systems both the regiochemistry and stereochemistry of the substitution are critical issues. The palladium normally bonds anti to the acetate leaving group. The same products are obtained from 2-acetoxy-4-phenyl-3-butene and 1 -acetoxy-l-phenyl-2-butene, indicating a common intermediate. The same product mixture is also obtained from the Z-reactants, indicating rapid ,Z-equilibration in the allylpalladium intermediate.118... 

An interesting gas-phase study of the photolysis of ftmy-l-phenyl-2-butene has been published by Comtet.(39,40) He has found that (a) it was not possible to quench the formation of the cyclopropane product under conditions that reduced the fluorescence quantum yield, (b) sensitization by acetophenone only gave cis-trans isomerization, and (c) the quantum yield of cyclopropane formation in the direct photolysis decreases as n-butane is added to the reaction mixture. Comtet suggests that the data are consistent with a reaction from the second triplet state. 

Cyanomethylamino)-l-phenyl-2-buten-l-one was cyclized in an exothermic reaction in ethanol in the presence of sodium ethylate. Then the reaction mixture was treated with mol. equiv. of acetic acid and EMME to... 

Scheme 6.141 Mechanistic proposal for the 121-catalyzed asymmetric intramolecular Michael addition exemplified for the model substrates ( )-4-hydroxy-l-phenyl-2-buten-l-one (n = 0) and ( )-5-hydroxy-l-phenyl-2-buten-l-one (n = 1) 121 functions as push/pull-type bifunctional catalyst inducing the cyclization of boronic acid hemiester (1) to form intermediate (2) release ofdiol product (3) by oxidation.

Disubstituted furans (130) can be obtained by treatment of j8-alkoxy- and j8-arylthio-a,j8-unsaturated ketones, for example 3-methoxy-l-phenyI-2-buten-l-one (128) or 3-ethylthio-l-phenyl-2-buten-l-one (129), with dimethylsulfonium methylide (79JHC815, 69TL679). The possible reaction pathway (Scheme 27) shows the initially formed epoxides as rearranging by ring opening at the tertiary epoxide carbon atom. 

The Michael addition of (2/ ,3S)-3,4-dimethyl-5,7-dioxo-2-phenylperhydro-1,4-oxazepine (236) to l-phenyl-2-buten-l-one (237) and 2-cyclopenten-l-one (238) in tetrahydrofuran at 0°C gave a mixture of diastereomeric... 

Z)-2-Fluoro-l-phenyl-2-butene (10%) also produced. 1-Chloro-3-methyl-2-phenylcyclopropane (25%) also produced. 

Mit Aryl-substituierten konjugierten Dienen liefert Natriumamalgam unter Isomerisie-rung l-Aryl-2-alkene. So bildet 1-Phenyl-1,3-butadien l-Phenyl-2-buten (70% d.Th., Kpi4 73°) und l,l,4,4-Tetraphenyl-l,3-butadien 1,1,4,4-Tetraphenyl-2-butens (F 141°) ... 

Chloral added with stirring to a suspension of 3-morpholino-l-phenyl-2-buten-1-one in benzene, and the homogeneous soln. formed by an exothermic reaction coned. 1-0X0-1-phenyl-3-morpholino-5-hydroxy-6,6,6-tridilorohex-2-ene. Y ... 

The Ti state (but not the Si state) of toluene sensitizes the photoisomerization of both ( )- and (Z)-2-heptene. Direct irradiation of either isomer of 1-phenyl-2-butene leads to photoisomerization. The fluorescence spectrum of l-phenyl-2-butene is simitar in shape to that of toluene but is slightly reduced in intensity. However, phosphorescence from 1-pheny 1-2-butene was not detected under conditions in which phosphoresence from toluene could readily be observed. Propose an explanation for the photoisomerization of l-phenyl-2-butene upon direct irradiation that is consistent with these observations. 

E)-l-Phenyl-2-buten-l-one added to a little dichloro[( + )-2,2 -bis(diphenylphos-phino)-l,r-binaphthyl]palladium(II) and 2 eqs. 1,1-dichloro-l-phenyl-2,2,2-tri-methyldisilane in benzene at room temp, under N2, the mixture refluxed for 2 h, cooled to —70°, treated with 1.9 M methyllithium in ether, stirred for 10 min then quenched with dil. HCl (S)-l-phenyl-3-(phenyldimethylsilyl)butan-l-one. Y 72% (87% e.e.). F.e. and conversion to p-hydroxyketones, also z //-a-alkyl-j3-hydroxy-derivs. by asym. 1,4-disilylation-alkylation, s. T. Hayashi et al., J. Am. Chem. Soc. 110, 5579-81 (1988) without asym. induction using Pd(PPh3)4 s. Tetrahedron Letters 29, 4147-50 (1988). 

PROBLEM 13.43 Why is it that ( )-l-phenyl-2-butene reacts only once with OSO4 Draw the product that is formed. 

Z)-l-Phenyl-2-butene This retrosynthesis suggests the following synthesis ... 

Styrene and ethylene were successfully codimerized by palladium chloride [49]. The major product was /ran -l-phenyl-1-butene (90%), but also 2-phenyl-2-butene (5%) and l-phenyl-2-butene (5%) were present (Equation 55). These codimers were obtained in yields up to 45%. 

---