1,3-Pentadiene phenylation

Dagegen reagiert 5-Phenyl-pentadien-(2,4)-saure-methylesterin einer 1,6-Addition zu 5-Phenyl-6-oxo-hep-ten-(2)-sdure-methylester (15% d.Th.)3 und unter 1,4-Addition zum 5-Phenyl-3,3-diacetyl-penten-(4)-sdure-methylester (30% d.Th.). 

Ebenfalls iiber einen Dreiring (Bis-[benzyliden]-cyclopropanon) verlauft die Reduktion von 2,4-Dibrom-3-oxo-l,5-diphenyl-l,4-pentadien in DMF [isoliert wild3-Oxo- 1,5-di-phenyl-penten-(4)-in-( 1)]. In Methanol hingegen bildet sich 5-Oxo-2,3-diphenyl-cydo-penten3. 

Ordinary Grignard reagents react with a, -unsaturated carbonyl compounds and afford both 1,2-adduct and 1,4-adduct. However, methylsulfonyhnethylmagnesium bromide or p-tolylsulfonylmethylmagnesium bromide gave only 1,2-adducts in the reaction with conjugated carbonyl compounds such as crotonaldehyde, cinnamaldehyde, trans-4-phenyl-3-buten-2-one, benzalacetophenone and l,5-diphenyl-2,4-pentadien-l-one. 

Tetramethoxypropadiene 88 or l-methoxy-l-(trimethylsilyl)-3-phenyl-l,2-pentadiene 89 may be easily protonated and then leads to dimethyl malonate or 1-tri-methylsilyl-3-phenyl-2-penten-l -one [42]. 

A combination of RuH2(PPh3)4 and ferrocenylphosphines catalyzes the crosscoupling reaction of a-hydroxyallenes and 1-alkynes to give exo-enynes selectively (Scheme 16.96) [102]. From the observation that O-protected allenes and 5-phenyl-1,2-pentadiene are inert to the cross-coupling reaction, the a-hydroxyl group in allenes plays an important role in this exo-selective reaction. 

If the quaternary nitrogen is a member of a ring, the ring is cleaved. 3-Benzyl-2-phenyl-A, A -dimethylpyrrolidinium chloride was cleaved by hydrogenation over Raney nickel at 20-25° almost quantitatively to 2-benzyl-4-dimethylamino-l-phenylbutane [722]. Reduction of methylpyridinium iodide (and its methyl homologs) with sodium aluminum hydride gave 24-89% yields of 5-methylamino-l,3-pentadiene (and its methyl homologs) in addition to A -methyl dihydro- and tetrahydropyridine [448]. 

Catalytic enantioselective synthesis of 4,4-dimethyl-l-phenyl-l,2-pentadiene from 4,4-dimethyl-1,2-pentadiene and iodobenzene using 0.4 to 1 mol % of palladium complexes containing chiral phosphane ligands as the catalyst for the enantioselective cross coupling134 is the only example of substoichiometric transition metal catalyzed enantioselective allene synthesis. 

Azadienes of this sort were studied simultaneously by Mariano et al., who reacted mixtures of (1 ,3 ) and (1E, 3Z)-l-phenyl-2-aza-l,3-pentadiene 275 with several electron-rich alkenes, e.g., enamines and enol ethers (85JOC5678) (Scheme 61). They found the (l ,3 )-stereoisomer to be reactive in this process affording stereoselectively endo 276 or exo 277 piperidine cycloadducts in 5-39% yield, after reductive work-up with sodium borohydride. The stereochemistry of the resulting adducts is in agreement with an endo transition state in the case of dienophiles lacking a cis alkyl substituent at the /8-carbon (n-butyl vinyl ether, benzyl vinyl ether, and 1-morpholino cyclopentene), whereas an exo transition state was involved when dihydropyrane or c/s-propenyl benzyl ether were used. Finally, the authors reported that cyclohexene and dimethyl acetylenedi-carboxylate failed to react with these unactivated 2-azadienes. 

Reaction of 2-cyanomethyl-4H-l,3-benzothiazin-4-one with benzoylace-tonitrile at 160°C yielded 8-cyano-7-imino-9-phenyl-7//,ll//-pyrido[2,l-6][l,3]benzothiazin-l 1-one (85MI1 86MI2). Reaction of 2-ethoxy-2,3 dihydro-4//-l,3-benzothiazin-4-one with 1,2,3,4-tetramethylbutadiene and 2,4-dimethyl-l,3-pentadiene in the presence of boron trifluoride in diethyl ether gave rise to 6,7,8,9-tetramethyl- and 7,9)9-trimethyl-5a,6,9,ll-tetrahydropyrido[2,l-6][l,3]benzothiazin-ll-one, respectively (73JHC149). 

Pentadiene 5-Phenyl-l.1.2-iriflnoi o-3-lrietliylsilyloxy-E10b,. 420 [SiR3 -ClKSiR,) -en — Ar)... 

Benzyl-2. ft-bis-[4-fl uoro-phenyl]-4-phcnyl- E7b. 937 (1.5-Pentadien-diolut + Ar —CH,-[)... 

The addition of HBr to 2-methyl-l,3-pentadiene, 1-bromo-1,3-butadiene, 1-phenyl-1,3-butadiene and 2,4-hexadiene produces 2,4-dibromo-2-methylpentane, 1,3-dibromo-l-butene, 3-bromo-l-phenyl-1-... 

A versatile method for the preparation of allyl complexes of transition elements involves addition of allyl halides or acetates to low oxidation state coordinatively unsaturated, or potentially unsaturated, complexes (214). A few attempts have been made to extend the method to halogenopentadienes. l-Chloro-5-phenyl-2,4-pentadiene adds to Pd2(dba)3 (dba = dibenzoylac-etone) to give the >/3-pentadienyl complex 61 [Eq. (30)] (215). A similar palladium complex has also been obtained from PdCl2, and 2,5-dimethyl-2,4-hexadiene in isopropanol (216). 

Pyridine and its derivatives react with 1,3-pentadienes forming cyclic products. This type of cyclization was observed by the authors of 95JFC(72)49. They showed that in the reaction of (Z)-1,1,2,5,5,5-hexafluoro-4-phenyl-3-trifluoromethyl-1,3-pentadiene 117 with pyridine the products are [ S,9aR]- and [lS,9tfS]-3-fluoro-9<2-hydro-l,2-bis(trifluoro-methyl)-l-phenyl-4//-quinolizin-4-ones 118 and 119 with 54 and 21% yields, respectively. The structure of the compounds was confirmed by X-ray analysis. Similarly, the reaction of (Z)-l,l,2,5,5,5-hexafluoro-4-iodo-3-trifhioromethyl-l,3-pentadiene 120 with 4-substituted pyridines gives the derivative of 4//-quinolizin-4-one 121 with quinoline, the product is derivative 122. 

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