Addition reactions Diels-Alder

The organotin maleate and maleate half-ester derivatives also exhibit this bleaching effect reportedly by a Diels-Alder addition reaction (18). The reaction is specific to the organotin maleates other organotin carboxylates containing normal dieneopltiles fail to produce similar results (19). 

Potential 2,5-dihydroxy compounds (185) exist in the dicarbonyl forms (186). Succinic anhydride (186 Z = O) on silylation is converted into 2,5-bis(trimethylsilyloxy)furan (187) the latter compound readily participates in Diels-Alder addition reactions (80TL3423). Reaction of thiosuccinic anhydride (186 Z = S) with the triphenylphosphorane Et02CH=PPh3 gives a product which exists in the aromatic form (188) (75LA1967). 

This trend is revealed, for example, by the rates of Diels-Alder addition reactions of anthracene, naphthacene, and pentacene, in which three, four, and five rings, respectively are linearly fused. The rate data are shown in Table 9.3. The same trend can be seen in the activation energy and the resonance energy gained when cycloreversion of the adducts 9-12 yields the aromatic compoimd, as shown in Scheme 9.3. 

Since both oxepin and its valence isomer benzene oxide contain a x-tb-diene structure they are prone to Diels-Alder addition reactions. The dienophiles 4-phenyl- and 4-methyl-4//-l,2,4-triazole-3,5-dione react with substituted oxepins at room temperature to give the 1 1 adducts 7 formed by addition to the diene structure of the respective benzene oxide.149 190,222... 

The addition of 2,3-dimethyl-1,3-butadiene to 17 gives only one structural isomer, 21. The pseudo-first order half-life of this Diels-Alder addition reaction is 47.5 minutes at 22.2°C in neat diene solution. The Ea of this reaction is estimated to be 9.2 kcal/mol. This reaction rate is 50 times faster than the rate of addition of this diene to methyl methacrylate (33). 

Note Added in Proof. The stereochemistry of the Diels-Alder addition reactions shown in Scheme 1 to give products 20-22 has been examined by 400 MHz lH-NMR. These data indicate that the cycloadditions occur with a high degree of stereoselectivity (having diastereoselectivities of greater than 94 6). The chiral Fe environment of the dienophile 17 strongly influences the direction of the facial attack of the diene reactants. 

Routes to benzo-fused derivatives of 1,4-dioxanes, 1,4-oxathianes and 1,4-dithianes make use of anions or dianions of the appropriate 1,2-disubstituted benzene. An alternative approach to the synthesis of 1,4-benzodioxanes involves Diels-Alder addition reactions of alkenes across the quinone function of 1,2-benzoquinones, e.g. (352) — (353). 

The metathesis polymerisation of dicyclopentadiene, an inexpensive monomer (commercially available cyclopentadiene dimer produced by a Diels-Alder addition reaction containing ca 95 % endo and ca 5 % exo form), leads to a polymer that may be transformed into a technically useful elastomer [144-146, 179] and thermosetting resin [180,181]. The polymerisation has characteristics that make it readily adaptable to the reaction injection moulding ( rim ) process [182], The main feature of this process comes from the fact that the polymerisation is carried out directly in the mould of the desired final product. The active metathesis catalyst is formed when two separate reactants, a precatalyst (tungsten-based) component and an activator (aluminium-based) component, are combined. Monomer streams containing one respective component are mixed directly just before entering the mould, and the polymerisation into a partly crosslinked material takes place directly in this mould (Figure 6.5) [147,168,183-186],... 

Tridentate salen ligands (10) derived from 1 have given excellent results in the enantiocontrol of the hetero Diels-Alder addition reaction of dienes with aldehydes (eq 7) and in the asymmetric additions of TMS-azide to mc5o-epoxide and trimethylsilyl cyanide to benzaldehyde (up to 85% ee). Phosphino-oxazolines derived from 1 have been employed for the asymmetric control of palladium-catalyzed allylic substitution reactions products of 70-90% ee were obtained. Photolysis of crystalline adducts of enantiomerically pure 1 with prochiral alcohols results in asymmetric inductions of up to 79% in a rare example of a solid-state enantioselective reaction. ... 

Other workers also have applied the Diels-Alder addition reaction to the preparation of angular-substituted derivatives of phenanthrene possibly obtainable as products of degradation of the morphine alkaloids. 

This phenomenon is well known in most cycloadditions, i.e., additions in which two components are combined which have two enantiofaces each. Thus altogether four combinations are possible leading to two enantiomeric pairs of exo-endo-diastereomers (Scheme 31) [Diels-Alder addition, reaction (94)]. In the arbitrary combination shown is in the endo- and R in the exo-position. Rndo-selectivity in the Diels-Alder reaction (and other cycloadditions) means that the substituent with the higher potential for 7t-7t-interactions with the diene... 

Mukaiyama T, Inubushi A, Suda S, Kara R, Kobayashi S (1990) Chem Lett 1015 Substituted aromatic solvents have been shown to have a dramamtic effect on the enan-tioselectivity of Ti TADDOL-catalyzed Diels Alder addition reactions, see Narasaka K, Iwasawa N, Inoue M, Yamada T, Nakashima M, Sugimori J (1989) J Am Chem Soc 111 5340... 

C. Chemical Properties 1. Diels-Alder Addition Reactions... 

The use of acyclic precursors by Claisen cyclisation or Diels-Alder addition reactions. 

S-Unsaturated hydrazones such as (12) have been shown to behave as 1 -aza-1, 3-dienes in Diels-Alder addition reactions with a range of dienophiles such as maleic anhydride (Scheme 2). The dimethylamino substituent in the cycloadducts (e.g. 13) may be cleaved by treatment with zinc and acetic acid, but no conditions have so far been found to cleave the N-N bond without reducing the C-C double bond 5-Nitropyrimidine undergoes inverse Diels-Alder cycloaddition with electron-rich dienophiles such as enamines and ketene N,N- and 0,0-acetals (Scheme 3). ... 

Solution The Diels-Alder addition reaction between... 

An interesting Diels Alder addition reaction is the addition of bismaleic imides to perylene ... 

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