Dienes synthesis from

Scheme 11. 1,3-Diene synthesis from alkyne and ethylene...

Diene synthesis from 2-alkyne-1,4,-diols with LAH (see 1st edition). 

C20 cyclic fatty acids of a slightly different type are produced by diene synthesis from a Cis conjugated diene acid and ethene. 

Dieck, H.A. and Heck, R.R (1975) A palladium-catalyzed conjugated diene synthesis from vinylic halides and olefinic compounds J. Org. Chem., 40, 1083-90. 

Startg. m. heated at 150° for 8 h - product. Y 70%. This is part of a sequential intermolecular-intramolecular diene synthesis from cyclopentadienones and dienes. F.e. and oxa-analogs s. K. Harano et al., Chem. Pharm. Bull. 36, 2312-22 (1988). 

Kinoshita A, Sakakibara N, Mori M. Novel 1,3-diene synthesis from alkyne and ethylene by ruthenium-catalyzed enyne metathesis. 7. Aw. Chem. Soc. 1997 119 12388-12389. 

Tonogaki K, Mori, M. An improved 1,3-diene synthesis from alkyne and ethylene using cross-enyne metathesis. Tetrahedron Lett. 2002 43 2235-2238. 

The mechanism of the diene synthesis appears to involve an electron transfer from the diene to the dienophile, .e., it is initiated by an ionic reaction. The following scheme may represent the addition of 2 3-dimethylbutadiene to maleic anhydride ... 

Danishefsky et al. were probably the first to observe that lanthanide complexes can catalyze the cycloaddition reaction of aldehydes with activated dienes [24]. The reaction of benzaldehyde la with activated conjugated dienes such as 2d was found to be catalyzed by Eu(hfc)3 16 giving up to 58% ee (Scheme 4.16). The ee of the cycloaddition products for other substrates was in the range 20-40% with 1 mol% loading of 16. Catalyst 16 has also been used for diastereoselective cycloaddition reactions using chiral 0-menthoxy-activated dienes derived from (-)-menthol, giving up to 84% de [24b,c] it has also been used for the synthesis of optically pure saccharides. 

The total synthesis of palytoxin (1) is a landmark scientific achievement. It not only extended the frontiers of target-oriented synthesis in terms of the size and complexity of the molecules, but also led to new discoveries and developments in the areas of synthetic methodology and conformational analysis. Among the most useful synthetic developments to emerge from this synthesis include the refinement of the NiCh/CrC -mediated coupling reaction between iodoolefins and aldehydes, the improvements and modifications of Suzuki s palladium-catalyzed diene synthesis, and the synthesis of A-acyl vinylogous ureas. 

Monodehydrohalogenation of allylic halides is another classical method for diene synthesis24. This method is complementary to double dehydrohalogenation as both the 1,2-dihalides and allylic halides are readily accessed from alkenes. The commonly employed protocol for diene synthesis, particularly for cyclic 1,3-dienes, is through the allylic monobromination of the alkene with A-bromosuccinimide or related reagents followed by dehydrobromination with hindered bases such as DBN or DBU (equation l)25. 

Trost and coworkers have devised a stereocontrolled 1,3-diene synthesis employing a palladium-catalysed decarboxylative elimination procedure from allylic acetates carrying carboxylic acid functionality ji- to the acetate group (equation 18)48. This decarboxylative elimination strategy has been applied to the synthesis of an insect pheromone, codlemone48a and the ethyl ester of vitamin A carboxylic acid (Table 5)48b. 

Enyne metathesis is unique and interesting in synthetic organic chemistry. Since it is difficult to control intermolecular enyne metathesis, this reaction is used as intramolecular enyne metathesis. There are two types of enyne metathesis one is caused by [2+2] cycloaddition of a multiple bond and transition metal carbene complex, and the other is an oxidative cyclization reaction caused by low-valent transition metals. In these cases, the alkyli-dene part migrates from alkene to alkyne carbon. Thus, this reaction is called an alkylidene migration reaction or a skeletal reorganization reaction. Many cyclized products having a diene moiety were obtained using intramolecular enyne metathesis. Very recently, intermolecular enyne metathesis has been developed between alkyne and ethylene as novel diene synthesis. 

Terminal allenes.1 A synthesis of 1,2-dienes (3) from an aldehyde or a ketone involves addition of ethynylmagnesium bromide followed by reaction of the adduct with methyl chloroformate. The product, a 3-methoxycarbonyloxy-l-alkyne (2), can be reduced to an allene by transfer hydrogenolysis with ammonium formate catalyzed by a zero-valent palladium complex of 1 and a trialkylphosphine. The choice of solvent is also important. Best results are obtained with THF at 20-30° or with DMF at 70°. 

Scheme 18.11 Synthesis of (R)-(—)-tricosa-9,l 0-diene (27a) from chiral propargylic alcohol 28 (AlBN = azobisisobutyronitrile) [37].

The student is recommended to carry out the Diels and Alder diene synthesis when making preparations from the original literature. For example, he should condense cyclo-hexadiene with quinone (Annalen. 1933, 507, 288) or furane with maleic anhydride (Ber., 1929, 62, 554). 

Scheme 26 Synthesis of (3R,5 )-2,6-dimethyl-2,3-epoxy-octa-5,7-diene, isolated from male Amblypelta nitida [121]...

The cation-radical version of diene synthesis, in which the diene is in a strongly electron-deficient state, is characterized by an unusual high endoselectivity. In this case, endoselectivity is sig-nihcantly higher than that of thermal or photochemical initiation of a neutral molecule (cf. Mlcoch and Steckhan 1987). As follows from the charge diagram depicted in Scheme 7.21, when a cation-radical and neutral molecule approach each other, not only the C(l)-C(6) and C(4)-C(5) interactions are bonding (indeed, these interactions result in cyclization), but C(2)-C(7) and C(3)-C(8) interactions are also bonding. As a result, the endo product is formed. 

Construction of 1,3-diene moieties from alkynes and ethylene is a unique methodology for the synthesis of 1,3-dienes. Mori used this strategy for the synthesis of anolignan A. Two methylene groups from ethylene are introduced onto the alkyne carbon of 109 using Ig to give 1,3-diene 110. From this compound, short-step synthesis of anolignan A is achieved (Scheme 41). ... 

Cyclopropane derivatives, including spiropentanc, have proven to be virtually inert towards carbenes,1 For this reason, no literature report that describes cyclobutane synthesis from a C3 and a Cj building block by ring enlargement of cyclopropanes exists. However, due to the partial p character, as well as the increasing reactivity caused by its strain, the central bond of bicyclo[1.1.0]butane (l)2 has been found to react with carbenes.1 Photolysis of diazomethane in the presence of bicyclo[1.1.0]butane (1) at — 50 C provides a mixture of several compounds. The major fraction of the material (80%) was analyzed by means of NMR spectrometry and found to consist of penta-1,4-diene (2, 21%) and bicyclo[l.l.l]pentane (3, 1%), plus several other known compounds as well as some unidentified products.3 The mechanistic pathway for the formation of bicyclo[l.l.l]pentane (3) has not been addressed in detail, but it is believed that a diradical intermediate is involved, as shown below.3... 

Diene synthesis.6 /3-Acetoxy carboxylic acids undergo loss of CH,COOH and C02 when refluxed in T1IF or DMSO in the presence of triethylamine (1 equivalent) and catalytic amounts of Pd(0). This fragmentation is highly stereoselective the (F.)-alkene is formed predominately, irrespective of the stereochemistry of the substrate. The method is particularly useful for stereocontrolled synthesis of 1,3-dicnes from stereoisomeric mixtures. 

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