Amino Diels-Alder-adduct with cyclopentadiene

The thermal decomposition of anthracene-9,10-biimine at 353 K is a straightforward way to get N2H2 [16, 20]. The similar 1,4 Diels-Alder adduct with cyclopentadiene may be a precursor of N2H2 [38]. 1-amino-2,2-diphenylaziridine decomposes at room temperature to give N2H2, perhaps as a result of an internal rearrangement of the primarily formed aminonitrene [39]. 

Formation.—Preparation of thietan oxides by oxidation of thietans is covered in the previous section. Cycloaddition of sulphenes to electron-rich alkenes, the other important method of preparation of episulphones, has been further used for the preparation of a-chloro- and /S-amino-, cf-sila- and -amino-, and cf-alkoxycarbonyl- and -amino-thietan dioxides. The sulphonyl enamine (96) can be converted into the thietan dioxide (97) by treatment with acid, a procedure that usually hydrolyses enamines to ketones. Regeneration of (96) from (97) occurs on heating in alcoholic base. Thiet sulphone cyclo-adds to cyclopentadiene to give the Diels-Alder adducts with an exo/endo ratio of 0.25. ... 

As shown in Table 26, the same selectivities were observed in the reactions of other 3-acyl-l,3-oxazolidin-2-ones. Thus, by using the same chiral source ((R)-(+)-binaphthol), both enantiomers of the Diels-Alder adducts between 3-acyl-l,3-oxazolidin-2-ones and cyclopentadiene were prepared. Traditional methods have required both enantiomers of chiral sources in order to prepare both enantiomers stereoselectively [74], but the counterparts of some chiral sources are of poor quality or are hard to obtain (for example, sugars, amino acids, alkaloids, etc.). It is noted that the chiral catalysts with reverse enantiofacial selectivities could be prepared by using the same chiral source and a choice of achiral ligands. 

Further X-my and electron diffraction studies are reported. Analysis of 3-diazocamphor by X-ray diffraction shows some contribution of the enolate which provides a means of stabilization by charge delocalization. The observed C-1—C-7—C-4 angle of 92° agrees well with values obtained earlier by diffraction methods and by analysis of the n.m.r. spectrum of partly oriented nor-bornadiene. The 2-aminonorbornane-2-carboxylic acids show biological activity in inhibiting the Na -independent transport of non-polar amino-acids across cell membranes. The structure of 2-exo-aminonorbornane-2-carboxylic acid has been determined. The adduct of cyclopentadiene dimer with N-sulphinylaniline has structure (50). As (50) was obtained after several crystallizations it is probable that other isomers, which have not been reported, are present in the reaction mixture and the reaction is not fully regiospecific. The structure of the photoadduct of the butadiene-p-benzoquinone Diels-Alder adduct has been confirmed by a diffraction study as (51). 

Fujisawa et al. [Ill] have reported that the magnesiiun complex prepared from chiral 2-[2-[(tolylsulfonyl)amino]phenyl]-4-phenyl-l,3-oxazoline 81 and methyl-magnesium iodide was efficient, in a stoechiometric amount, for promoting the enantioselective Diels-Alder reaction of 3-alkenoyl-l,3-oxazohdin-2-one with cyclopentadiene (Scheme 45) leading exclusively to the endo adducts in up to 92% ee. The use of 10 mol% of the complex led to an important decrease in enantioselectivity of the product (51% ee). 

Copper(II) complexes of amino acids have been explored as chiral Lewis acid catalysts in the Diels-Alder reaction of 3-phenyl-l-(2-pyridyl)-2-propen-l-one with cyclopentadiene. The best results were obtained using /V-methyl-/.-tryptophan, but more interestingly, the highest ee values for the major endo adduct were achieved in aqueous solution273. 

Mukaiyama and co-workers have reported that prolinol derivatives combined with BBrs produce promising catalysts for some Diels-Alder reactions [26]. Methacrolein and cyclopentadiene, for example, afford the exo adduct (exoiendo > 99 1) in 97 % ee (reaction at -78 °C in dichloromethane with 20 mol % catalyst). The chiral catalyst is believed to be the HBr adduct salt of the amino boron derivative (Eq. 26). 

In 1974, Jagt and Van Leusen (74JOC564) found that sulfonyl cyanides are good dienophiles. At room temperature, tosyl cyanide (67) dissolved in cyclopentadiene 68 is converted into 3-tosyl-2-azabicyclo [2.2.1 ]hepta-2,5-diene (69) (95%). This is the first example of the formation of a primary Diels-Alder cycloadduct of a nitrile. Adduct 69 was hydrolyzed with acetic acid and water to the lactam 70. Daluge and Vince (73JOC2311) used 70 to synthesize puromycin analog 76 (Scheme 9). Lactam 70 was hydrolyzed to the cis-amino... 

The model reaction to be mediated by hybrid catalysts comprised of 32/serum albumins, was the Diels-Alder reaction of the H O-soluble aza-chalcone 33 with cyclopentadiene 34 with formation of chiral adducts 35. This reaction had been originally devised by Engberts [123, 124], who used Cu -complexes of amino acids in aqueous medium ee up to 74%). Later it was employed by Feringa in the study of Cu -conjugates of DNA as catalysts [125]. 

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