Glycoluril

Molecular and supramolecular objects from glycoluril, 2,4,6,8-tetraazabicyclo-[3.3.0]octan-3,7-dione 99ACR995. 

Sijbesma, R. P., Nolte, R. J. M. Molecular Clips and Cages Derived from Glycoluril. 175, 57-100 (1995). 

Figure 2. Left Family of softball" monomers 4-7. Different spacers between the centerpiece and the glycoluril binding sites permit assembly of dimers with cavity volumes between 186 A3 and 313 A3. Right Computer-minimized...

Figure 4. Left Softball monomers BO and 31 with two different glycoluril arms" and de values (%) obtained for encapsulation of guests 32 - 36 in 30-30 and 31 31. Right Schematic representation of the two enantiomeric...

Chlorinated fluorocarbons (CFCs), 21 591 Chlorinated glycolurils, 73 109-110 Chlorinated hydantoins, 13 110 Chlorinated hydrocarbons (CHC) contamination by, 23 111—112 for PVC polymers, 25 674 Chlorinated isocyanurates end use of chlorine, 6 135t as pool sanitizers, 26 175-176 Chlorinated methanes... 

The crosslinkers examined in this study were aminoplast resins 1-4 selected from melamine-formaldehyde, urea-formaldehyde, benzoguanamine-formaldehyde, and glycoluril-formaldehyde resins, all of which undergo the crosslinking sequence shown in Scheme 1. The response of these crosslinkers to acid catalysis in thin films is compared on a relative basis to the well studied methylated melamine, 1 19-11). 

Burnett CA, Lagona J, Wu A, Shaw JA, Coady D, Fettinger JC, Dayb AI, Isaacs L (2003) Preparation of glycoluril monomers for expanded cucurbit[n]uril synthesis. Tetrahedron 59 1961-1970... 

Witt, D. Lagona, J. Damkaci, F Fettinger, J. C. Isaacs, L. Diastereoselective formation of methylene-bridged glycoluril dimers. Org. Lett. 2000, 2,755-758. 

More recently, Wu et a/. <2006JOC4502> have described an extensive crystallographic study of 11 different molecular clips based on the glycoluril skeleton 11. 

Their research has focused on examining the effect of substitution on the aromatic ring in the crystal state. Their results show that different substitution leads to different structures being formed in the crystal state. They conclude that even weak intermolecular interactions such as C-H-O hydrogen bonds can be used to control crystal packing within glycoluril systems. 

The vast majority of the reactions of the 5-5 fused systems have been the alkylation of nitrogen atoms by electrophiles and oxidants. Most of the examples have been in the alkylation of glycoluril derivatives and the general methods have been extensively covered in CHEC(1984) and CHEC-II(1996) and as such do not generally require comment here. Some of the alternative and less common methods however are outlined below. 

Nitrosation of glycoluril derivatives has also been reported by simple exposure to nitric acid and sodium nitrite (Equation 11) <1998RJOC34>. 

Reductions of these ring systems are common. Most often, active hydrogen techniques are employed to cleave weak heteroatom-heteroatom bonds. Reductions of the glycoluril derivatives are less common due to the lack of such a weak bond. Some recent examples include reactions by Chan et al. <2003TL395> who employed Raney nickel and hydrogen to effect cleavage of an N-O bond in their synthesis of new heterocyclic compounds via 1,3-dipolar cycloaddition chemistry (Equation 15). 

Harrison et al. have demonstrated that bis-acyl glycoluril derivatives 84 undergo efficient Claisen ester condensation, as exemplified in Equation (18) to yield /3-ketoamide derivatives 85. A kinetic study is also presented which indicates clean, bimolecular kinetics and short half lives for the intermediates <2002CJC517>. 

By far, the greatest interest in 5-5 heterocyclic systems containing two heteroatoms in each ring has been in the field of supramolecular chemistry and in the preparation of molecular receptors of various types. One of the most widely used heterocyclic backbones for these receptors has been glycoluril 5 and its derivatives. 

Although noted by both Nolte <1995TCC25> and Rebek <1995S1485> that these systems are ideal scaffolds for the preparation of molecular receptors, it is only in recent years that interest in these systems has increased and a number of significant advances have been made in what is now an intense field of research. In particular, Nolte noted that glycoluril possesses many desirable characteristics for elaboration into a molecular receptor including ... 

One of the major applications of glycolurils is in the preparation of the cucurbituril family of molecular receptors. Despite being known for a number of years the popularity of this molecule has grown significantly in the last decade. The most common member of the cucurbituril family is cucurbit[6]uril containing six glycoluril units linked by methylene units 149 (Figure 6). 

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