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Reaction of ketenes with N,N ‐disubstituted α‐aminomethyleneketones. XIX . Synthesis of N,N ‐disubstituted 4‐amino‐3‐phenyl‐2 H ‐furo[2,3‐ h] ‐1‐benzopyran‐2‐ones (4‐amino‐3‐phenylangelicins). Crystal and molecular structure of 3‐Phenylangelicin
Author(s) -
Mosti Luisa,
Sche Pietro,
Menozzi Giulia,
Sancassan Fernando,
Baccichetti Francarosa,
Benetollo Franco,
Bombieri Gabriella
Publication year - 1988
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570250211
Subject(s) - chemistry , cycloaddition , substituent , moiety , benzopyran , crystal structure , dihedral angle , reagent , stereochemistry , hydrogenolysis , medicinal chemistry , molecule , crystallography , organic chemistry , catalysis , hydrogen bond
1,4‐Cycloaddition of phenylchloroketene to N,N ‐disubstituted 5‐aminomethylene‐6,7‐dihydrobenzo[ b ]‐ furan‐4(5 H )‐ones gave the corresponding adducts, namely N,N ‐disubstituted 4‐amino‐3‐chloro‐3,4,5,6‐tetra‐ hydro‐3‐phenyl‐2 H ‐furo[2,3‐ h ]‐l‐benzopyran‐2‐ones II , which were dehydrochlorinated with DBN to N,N ‐disubstituted 4‐amino‐5,6‐dihydro‐3‐phenyl‐2 H ‐furo[2,3‐ h ]‐1‐benzopyran‐2‐ones III . Compounds III afforded the title compounds IV by dehydrogenation with DDQ. In the cycloaddition step, 3‐phenylangelicin V , whose structure was confirmed by 1 H‐nmr shift reagents data and by X‐ray crystal structure determination, was almost always formed, probably starting from II by dehydrochlorination, dehydrogenation and hydrogenolysis of the disubstituted amino group. Separation of V was achieved by alumina chromatography either in the cycloaddition step or, in most cases, in the dehydrochlorination step. 3‐Phenylangelicin crystallizes in the trigonal system, space group R3, with cell parameters (hexagonal axes) a = b = 41.021(10), c = 3.888(2) Å. The angelicin moiety forms a dihedral angle of 42.1(1)° with the phenyl substituent. Disordered solvent molecules of ethyl acetate are clathrated in channels in the direction of the crystallographic axis c.