Dieh alder reaction

If a C=C bond is formally substituted for C=N, the reaction could proceed analogously however, it would require accessible aminoacety-lenes. Reagents of this type exist (e.g., N,N-diethylpropin-l-amine 79), and react with a,/l-unsaturated ketones 26 without a catalyst in inert solvents (73JHC165). This is a convenient approach toward 2-N,N-dialkylamino-4H-pyrans 80 and 81, which are formed, probably, via the hetero-Dieh-Alder reaction (Scheme 22). 

The reactivities of the diene and dienophile in a Diels-Akier reac tion are highly dependent on their electronic structures.15 In the case of a Dieh-Alder reaction with normal electron demand, the dienophile is substituted with an electron acceptor Z, whereas the dienophile carries an electron donor X. The reaction in question follows this pattern. Increased reactivity in such a case can be rationalized with the frontier orbital theory of hukui and HouL according to which the energy difference between the (HOMO) of the diene and the lowest unoccupied molecular orbital (LUMO) of the dienophile is reduced in a favorable way by the substituents. 

Asymmetric Dieh-Alder Reactions. The commercial availability of either enantiomer of camphorsulfonic acid has made it quite useful in asymmetric Diels-Alder reactions. Reaction of the sultone (generated from CS A) with Lithium Diisopropylamide followed by esterification and (3-elimination yields the crystalline acrylate (eq 14). The Lewis acid-catalyzed [4 + 2] cycloaddition of 1,3-dienes with this acrylate affords the corresponding scalemic adduct which can be reduced with Lithium Aluminum Hydride to yield an enantiomerically pure alcohol (eq 15). ... 

Dieh-Alder reaction whk thiophene. Helder and Wynberg have reported the first successful Diels Alder reaction of thiophenes using dicyanoacetylene as the dienophile. Thus 2,5-dimethylthiophene (I) when heated for 12 hr. in a closed tube at 100° with an excess of freshly prepared dicyanoacetylene yields 3,6-dimethylphthalonitrile (2)... 

Enantioselective Dieh-Alder reaction.3 The reaction of the chiral acrylate ester 1 with butadiene catalyzed with this Lewis acid followed by hydride reduction gives the alcohol 2 in 70% chemical yield and 86-91% ee. A1C13 and SnCl4 are inferior in terms of either the chemical or optical yield. The product (2) was used for a chiral synthesis of (R)-( — )-sarkomycin (4). 

Dieh-Alder reaction. BINAP-Pt(II) complexes with perchlorate and hexafluoroantimonate counterions are highly effective catalysts for the enantioselective Diels-Alder reaction. The corresponding Pd(II) complexes have comparable (and for certain substrates, somewhat inferior) reactivity. 

Dieh-Alder reactions with benzyne. Shepard has recently demonstrated that benzyne generated from chlorobenzene and LiTMP undergoes expected Diels-Alder cycloadditions with reactive dienes. The reaction with furane itself fails because of a base-promoted side reaction. 

Oikawa H, Yokota T, Ichihara A, Sakamura S (1989) Structure and Absolute Configuration of Solanapyrone-D - A New Clue to the Occurrence of Biological Dieh-Alder Reactions. J Chem Soc Chem Commun 1284... 

I 3S Diels-Alder and Hetero-Dieh-Alder Reactions... 

Dieh-Alder nactiota- Although 2.4-hcxadicne shows only slight regioiselee-tivity in Diek Alder reactions, the l aceioxy derivative (1) undergoes regknelective cydoaddition with a variety of dienophiles. ... 

Tandem Rh(I)-catalyzed Alder-ene/Dieh-Alder/Diels-Alder reaction of487i ... 

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