Diels’ diene synthesis

Compounds containing a double or triple bond, usually activated by additional unsaturation (carbonyl, cyano, nitro, phenyl, etc.) In the ap position, add to the I 4-positions of a conjugated (buta-1 3-diene) system with the formation of a ax-membered ring. The ethylenic or acetylenic compound is known as the dieTwphile and the second reactant as the diene the product is the adduct. The addition is generally termed the Diels-Alder reaction or the diene synthesis. The product in the case of an ethylenic dienophile is a cyctohexene and in that of an acetylenic dienophile is a cyctohexa-1 4-diene. The active unsaturated portion of the dienophile, or that of the diene, or those in both, may be involved in rings the adduct is then polycyclic. 

In the Diels-Alder reaction (in older literature referred to as the diene synthesis ) a six-membered ring is fonned through fusion of a four-tt component, usually a diene and a two-7C component, which is commonly referred to as the dienophile (Scheme 1.1). 

The synthesis of natural products containing the quinonoid stmcture has led to intensive and extensive study of the classic diene synthesis (77). The Diels-Alder cycloaddition of quinonoid dienophiles has been reported for a wide range of dienes (78—80). Reaction of (2) with cyclopentadiene yields (79) [1200-89-1] and (80) [5439-22-5]. The analogous 1,3-cyclohexadiene adducts have been the subject of C-nmr and x-ray studies, which indicate the endo—anti—endo stereostmcture (81). 

O. Diels (Kiel) and K. Alder (Cologne) discovery and development of the diene synthesis. 

The reaction investigated by Diels and Alder in 1928 was not new, examples had been known for several years [6]. Early work on the dimerization of tetra-chloropentadienone was conducted by Zincke in 1893 and 1897. In 1906, Albrecht described the product of addition of p-benzoquinone to one or two molecules of cyclopentadiene. Albrecht assigned erroneous formulas to these addition products, but they were later shown to be typical products of the diene synthesis by Diels and Alder. Ruler and Josephson reported the addition products formed by iso-prene and 1,4-benzoquinone in 1920. This research laid the ground work for Diels and Alder. 

The choice of the acyl substituent X for Diels-Alder reactions of l-N-acylamino-l,3-butadicnes depends on the particular synthetic problem. The acyl substituent has a moderate effect on the cycloaddition reactivity of these dienes, and also determines what amine unmasking procedures are required. As a result of their stability and the variety of amine deprotection procedures available, " the diene carbamates are the components of choice in most cases. A particularly attractive aspect of the diene synthesis detailed here is the ability to tailor the amino-protecting group... 

Recently, Jankowski et al. [80] reported the application of MW to the Diels-Alder synthesis of N-methyloctahydroisoquinoline adducts, which are important intermediates in the synthesis of medicinally important compounds, such as HIV protease inhibitor isoquinoline carboxylate pharmaceuticals. The reaction of the arecoline 67 or its isomer 70 with Danishefsky s diene 68 in toluene (Scheme 4.32) was studied under both conventional and MW heating in sealed tubes, i. e. at elevated pressure. 

Generally, benzene and naphthalene derivatives show only little reactivity as dienes in Diels-Alder synthesis, contrary to anthracene and the higher acene derivatives which are frequently used as dienes. Exceptions are the reactions of benzene and naphthalene derivatives with highly reactive dienophiles such as dicyanoacetylene (DCA), which... 

It has long been known that unsaturated compounds containing a delocalized system of 71 electrons can rearrange into cyclic compounds or other n systems. Such reactions were only incidentally studied until 1930. 0. Diels and K. Alder published their first paper on diene synthesis (which was later given the name Diels-Alder reaction) in 1928. Subsequent work of K. Alder and G. Stein (1933 and 1937) proved the generality of the reaction and its high regio and stereo selectivity. This led to the interest on thermal transformations in unsaturated compounds. 

Wasserman, A. Diels-alder reactions. New York Elsevier 1965 Onishchenko, A. S. Diene synthesis. Israel, Jerusalem S. Monson Binding 1964 Sauer, J., Wiest, H., Mielert, A. Z. Naturforsch. 17B, 203 (1962)... 

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). 

Alder, K. Pascher, F. Schmitz, A. Ber. Dtsch. Chem. Ges. 1943, 76, 27. Kurt Alder (Germany, 1902—1958) shared the Nobel Prize in Chemistry in 1950 with his teacher Otto Diels (Germany, 1876—1954) for development of the diene synthesis. 

Now, dienes with shielded donble bonds can be involved in diene synthesis. The presence of donor gronps at the double bond normally prevents its involvement in conventional Diels-Alder condensations. These reactions do take place with the cation-radicals. Cyclic adducts are formed in high yields (80-90%) and under mild conditions. Polymerization, which usnally decreases the yield is inhibited completely within the framework of the cation-radical variant (Bellville et al. 1981). The stereoselectivity of the addition, which is usually typical for diene condensation, does not change in the cation-radical version and even increases. The positional selectivity also increases. The regiose-lectivity is enhanced, as well. Bauld et al. have discovered and explained these effects (Bellville and Banld 1982, Bellville et al. 1981, 1983, Banld and Pabon 1983, Pabon and Banld 1984). 

Dichlorodibutyl ether, 27 Diels-Alder reaction of butadiene with maleic anhydride, 93 Diene synthesis of cis-A -tetrahydro-phthalic anhydride, 93 Diethyl benzalmalonate, 84 Diethyl carbonate, 44 Diethyl fumarate, 46 Diethyl cis-HEXAiiYDROPiiTHALATE, 29 Diethyl malonate, 70 Diethyl o-nitrobenzoylmalonatc, 71 Diethyl sodium phthalimidomalonate, 7... 

Diels-Alder Synthesis. An additive combination of "dienes "(qv) with substances of the grouping >C=C-CO-R. For the description of this synthesis see Refs... 

Dicyanopentane, 493 Dict/clohexyl, 21, 470 Dieckmann reaction, 856, 857 Diels-Alder reaction, 941, 942J, 943 Diene synthesis, 941, 942, 943 P-Diethylaminopropionitrile, 915, 917... 

This method affords a-pyrone in quantity and in good yield not achieved previously.3 The compound has considerable possibilities in Diels-Alder reactions, such as a decarboxylative double diene synthesis.5... 

T he well-known 1,4-cycloaddition reaction of a 1,3-diene to a dieneo-A phile which forms a six-membered adduct, commonly known as the Diels-Alder reaction, or diene synthesis, is established as a useful synthetic organic reaction. Although this reaction provides a high yield of... 

The usual reaction of alkenes with conjugated dienes is the Diels-Alder synthesis. This addition does not apply, with a few exceptions, to cycloaddition of fluorinated alkenes. The presence of fluorine atoms, especially if there are more of them around the double bond, retards the cycloadditions forming six-membered rings, and accelerates the (2 + 2) cycloaddition to form four-membered rings. 

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