[Reaction of conjugated systems containing nitrogen. IV. Reaction of conjugated 1,2-diimines with isocyanates]

Synthesis of glycolurils and their analogues

Glycolurils — tetrahydroimidazo[4,5-d]imidazole-2,5(1H,3H)-diones — have found widespread applications in various fields of science and technology. Among them, there are pharmacologically active compounds (antibacterial, nootropic, neurotropic agents, etc.), explosives, gelators, etc. They are used as building blocks in supramolecular chemistry. Therefore, the development of new methods for the synthesis of glycolurils and their analogues has constantly attracted the attention of researchers. In this review, we analyze various approaches to the synthesis of glycolurils and their analogues. The review covers both classical reactions of ureas and related compounds with α-dicarbonyl compounds or with 4,5-dihydroxyimida-zolidin-2-ones (-thiones) and their imino analogues and new original reactions of 4,5-dihydroxyimidazolidin-2-ones (-thiones), imidazolinones and their bicyclic analogues with ureas and KNCS in the presence of acids, condensations of 1,4-disubstituted 1,4-diaza-1,3-dienes with isocyanic and/or isothiocyanic acids or isocyanates, triazine ring contraction in imidazotriazines to give the imidazolidine ring, and transformations of urazoles.

The bibliography includes 129 references.

Criss-cross cycloadditions on ketazines derived from alicyclic ketones

The reactivity of alicyclic ketazines in criss-cross cycloadditions was investigated. They react with potassium cyanate and ammonium thiocyanate in the presence of acetic acid to form spirocyclic perhydro[1,2,4]triazolo[1,2-alpha][1,2,4]triazole-1,5-diones and perhydro[1,2,4]triazolo[1,2-alpha][1,2,4]triazole-1,5-dithiones, respectively, in relatively high yields.

Aromatic glyoxalimines in criss-cross cycloaddition reactions

Aromatic 1,4-diazabuta-1,3-dienes in glacial acetic acid with thiocyanates produce via criss-cross cycloaddition reactions the corresponding perhydroimidazo[4,5-d]imidazole-2,5-dithiones. When a mixture of thiocyanate and cyanate in a proper ratio was reacted together, nonsymmetrical 5-thioxo-perhydroimidazo[4,5-d]imidazole-2-ones were isolated. With cyanates substituted aromatic 1,4-diazabuta-1,3-dienes afforded product of acetic acid addition to primary formed 1,3-dipole intermediate 5-(4-substituted phenylamino)-3-(4-substituted phenyl)-2-oxoimidazolidin-4-yl acetate.

The Chemistry of Pericyclic Reactions and Their Application to Syntheses of Heterocyclic Compounds

Diels-Alder reactions of benzylidenecyanomethyl-1,3-benzothiazoles 17 and -1,3-benzoxazoles 18 as 1-aza-1,3-butadienes are described. The dienes 17 and 18 featuring stabilized imine moieties in the form of heteroaromatic rings react with both electron-deficient and electron-rich dienophiles to give corresponding cycloadducts regioselectively. The cycloadditions of the intramolecular systems 34c,d and 35c,d proceeded smoothly via the exo-transition state, stereoselectively affording polycyclic compounds 36c,d and 37c,d in good to excellent yields. The diene systems of 17 and 18 were extended to dienes 19a-c with ester groups at diene-4-positions. Dienes 19a-c exhibited high Diels-Alder reactivities with electron-rich alkenes. Dienes 19a-c also reacted with allyl alcohols 55-58 in the presence of stanoxane catalyst 53 to give cycloadducts 59-62 via transesterification and intramolecular cycloaddition. Although alpha-alkoxycarbonylnitrones 64 have been very attractive nitrones for the syntheses of amino acids, the nitrones 64 exist as equilibrating mixtures of (E)-64 and (Z)-64. To solve this problem, three methods were explored: 1) sequential transesterification and intermolecular cycloaddition of nitrones 64 with allyl alcohols; 2) use of chiral and geometry-fixed nitrone 84; and 3) selective activation of (Z)-64 by Eu(fod)3. These methods were applied to syntheses of nikkomycins, clavalanine, and beta-substituted alpha-amino acids. The reactions of photoinduced carbonyl ylides from alpha,beta-unsaturated gamma,delta-epoxy nitriles were studied. Direct irradiation (lambda = 254 nm) of (E)-129 led selectively to products arising from the carbonyl ylide XXV or the carbene intermediate XXVI. The carbonyl ylides generated from (E)-129, (E)-139, and (Z)-143 were trapped with MeOH in the presence of amine, affording the corresponding acetals in moderate yields (Schemes 42 and 43). Photocyclization reactions of delta-hydroxyalkyl epoxy nitriles 148a-e led to spiro acetals arising from the carbonyl ylides (Scheme 45). The photoinduced carbonyl ylides from the epoxy dinitriles 158 and 160-163 underwent 1,3-dipolar cycloaddition with enol ethers, leading to a tetrahydrofuran system (Schemes 49 and 50, Table 14). Electrocyclization of 3-butadienylindoles 184 to intermediary dihydrocarbazoles XXXII followed by elimination of MeOH gave 3-oxyganated carbazoles 185, which were transformed to carbazole alkaloids hyellazole 168, 4-demethoxycarbazomycin B 170 and carazostatin 171, respectively. Claisen rearrangement of 3-(1-amino-1-vinyloxy) indolines derived from 3-hydroxyindolines 192 and amide acetal 193 gave indol-4-ylacetamides 194, which was reduced to afford 4-(2-aminoethyl) indoles 198, which has a framework of biologically active 4-substituted indole compounds. Claisen rearrangement of 3-allyloxyindoles produced in situ by condensation of indolin-3-ones 202 with allyl alcohols 203 and 206-211 gave 2-allylindolin-3-ones 204, 205 and 212-220. The domino reactions, Horner-Wadsworth-Emmons olefination of 2-allyloxyindole 233, isomerization, and Claisen rearrangement produced 3-allylindolin-2-one 234, which was derivatized to 3a-allylpyrrolo [2,3-b] indole alkaloid, flustramine C 221. Reverse aromatic Cope rearrangement of 2-allyl-3-indolidene acetonitriles 241-243, formed by Horner-Wadsworth-Emmons reaction of 2-allylindolin-3-ones 238-240, afforded indoles 244-246.