Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• method for the synthesis of pyrimidines containing an allomaltol unit. The suggested approach is based on the reaction of 2-(1-(dimethylamino)-3-oxo-3-arylprop-1-en-2-yl)-3-hydroxy-6-methyl-4H-pyran-4-ones with cyanamide. The photochemical behavior of the obtained pyrimidines was investigated. It was

• proposed. Keywords: allomaltol; dihydrobenzo[h]pyrano[2,3-f]quinazolines; 6π-electrocyclization; photocyclization; pyrimidines; Introduction Photochemical processes involve absorption of UV light leading to the generation of molecules in the excited state and subsequent chemical transformations [1][2

• ]. Among them, photoreactions of compounds containing the 3-hydroxypyran-4-one (allomaltol) fragment attract considerable attention due to the unique photochemical properties of compounds of this class. Previously it was shown that allomaltol derivatives under UV irradiation undergo contraction of the

A study of the photochemical behavior of terarylenes containing allomaltol and pyrazole fragments

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2022, 18, 588–596, doi:10.3762/bjoc.18.61

• established by X-ray diffraction. Keywords: allomaltol; ESIPT process; photochemistry; pyrazoles; terarylenes; Introduction The investigation of the photochemical behavior of organic products is a significant part of modern materials science and technology. The UV-induced processes are extensively employed

• two stages: 6π-electrocyclization of 1,3,5-hexatriene systems and subsequent aromatization of the central benzene ring. Among the significant diversity of terarylenes, compounds containing a 5-hydroxy-2-methyl-4H-pyran-4-one (allomaltol) fragment are of particular interest. For such systems two types

• processes can be complicated if additional photosensitive fragments are presented in the structure. For example, we previously studied the photochemical behavior of oxazolone terarylenes 9 containing the allomaltol fragment (Scheme 1C) [26]. It has been shown that UV irradiation of such systems leads to a

Synthesis of sulfur karrikin bioisosteres as potential neuroprotectives

• Martin Pošta,
• Václav Zima,
• Lenka Poštová Slavětínská,
• Marika Matoušová and
• Petr Beier

Beilstein J. Org. Chem. 2022, 18, 549–554, doi:10.3762/bjoc.18.57

• , derived from the 2H-furo[2,3-c]pyran-2-thione core, differing in the number and the position of methyl groups (9–12), has been prepared from appropriate karrikins. Starting materials, karrikins KAR1 (1), KAR3 (3) and KAR4 (4) (Figure 1) were synthesized from pyromeconic acid (5), allomaltol (13) or maltol

• pyromeconic acid (5) [26] and allomaltol (13) [27]. Unfortunately, the treatment of hydroxypyranones 5, 13 and 14 with Lawesson’s reagent resulted in an inseparable mixture (approx. 1:1) of pyranthiones 6a, 15a, 16a and thiopyranthiones 6b, 15b, 16b in low yields up to 30% in all the cases. In order to