Bis cyclic ureas

An efficient, practical solid-phase synthesis of a variety of bis-hetero-cyclic compounds was developed starting from resin-bound orthogonally protected lysine (Fig. 10). Tetraamines 36 were synthesized by exhaustive reduction of resin-bound tetraamides 35. Cyclization with different commercially available bifunctional reagents such as cyanogen bromide, thio-carbonyldiimidazole, carbonyldiimidazole, and oxalyldiimidazole yielded the corresponding bis-heterocyclic compounds bis-cyclic guanidines 37,39 bis-cyclic thioureas 38, bis-cyclic ureas 39, and bis-diketopiperazines 40, respectively.40 Reduction of compounds 40 led to bis-piperazines 41. 

A basket-shaped host that is a crown ether containing a bi-cyclic urea structure (7.6) (where R is phenyl) has been used to bind the herbicide Paraquat analogue (7.7) (where the anion is hexafluorophosphate) and some polymeric derivatives of it with iPup to 57,000.63 Even stronger binding with a Kof 7 million has been obtained with a cyclic urea porphyrin.64... 

The utility of the bis cyclic ureas for curing of coatings was demonstrated by dispersing them in a functional acrylic polymer formulated for powder coating application, or by using them as additive in solvent based coatings or in aqueous polymer emulsions for electrocoating. 

To achieve good compatibility with functionalized acrylic and epoxy resins a bis cyclic urea with n=3> and R=-(CH2)7-(see Scheme I) was synthesized. Acrylic- and epoxypolymer solutions were prepared using 15% by weight of the bis cyclic urea (based on the dry polymer) and methyl ethyl ketone as solvent. Films cast from these solutions on steel sheets were clear, and had a thickness of 0.4 mil. 

Indicated below are the baking temperatures for the films to become insoluble in methyl ethyl ketone using a 30 minute baking cycle. The required temperatures were lower by adding a catalyst 15% by weight based on the bis cyclic urea of dibutyltin dilaurate). 

More recently, systems have been reported which thermally generate isocyanates without the evolution of side products. When these thermal reactions are carried out in the presence of polyols, cured polyurethanes are said to be produced. One such system is based on bis(cyclic ureas). 

Eaton and co-workers ° synthesized the cubane-based dinitrourea (42) via iV-nitration of the cyclic urea (41) with nitric acid-acetic anhydride. Cubane-based nitramide (43) is prepared from the IV-nitration of the corresponding bis-amide with acetic anhydride-nitric acid. Bis-nitramine (44) is prepared from the IV-nitration of the corresponding diamine with TFAA-nitric acid. ... 

With AT, AT -bis(trifluoromethyl)urea, the corresponding cyclic intermediate has been isolated and characterized (148). The preparation and purification of SF5NCO are greatly simplified by first preparing SF5-NHC(0)F from an equimolar reaction mixture of NSF3, COF2, and AHF (149), followed by dehydrofluorination (150,151). 

Generation of 10 from the corresponding bis(iminophosphorane) using B0C2O in the presence of DMAP, resulted in the formation of the corresponding cyclic urea derivative. However, low yields of 10 are also obtained from bis(iminophhosphoranes) and isothiocyanates. 

Debnath, A.K. (1998). Comparative Molecular Field Analysis (CoMFA) of a Series of Symmetrical Bis-Benzamide Cyclic Urea Derivatives as HIV-1 Protease Inhibitors. J.Chem.Inf.Com-put.ScL, 38,761-767. 

Bis-urethanes derived from propylenediamines are converted to cyclic ureas... 

To address more challenging aUcene substrates, Widenhoefer [127] showed in 2009 that cyclic ureas could be used as spedahzed substrates for the hydroureation of completely unactivated alkenes, including ethylene (as mentioned in Section 15.3.2), propylene, terminal alkenes, and the strained internal alkene of nor-bornene. Using the preferred chiral bis(gold)phosphine catalysts (68), enantiomeric excesses of up to 78% have been obtained for this challenging transformation (Scheme 15.85) [127]. 

Epoxides can be readily formed using the standard Mitsunobu reaction conditions. A recent example (88) from the literature is shown below. The reader is referred to the cited paper for additional examples. Bis-epoxides such as 89 were useful in the preparation of a series of cyclic urea based HIV protease inhibitors. 

Cyclic urea-formaldehyde products that have been of commercial importance as crosslinking reagents are N,iV -bis(hydroxymethyl)-2-imidazolidone (2 jV,AT -dimethylolethyleneurea, DMEU) and N,N -bis(hydroxymethyl)-4,5-dihydroxy-2-imidazolidone (3 7V,iV -dimethyloldihydroxy-ethyleneurea, (DMDHEU). 

Of particular interest in the latter case is the use of N-NMR spectroscopy for the determination of J( P, N) data, of which there are few examples for systems having two coordinate sp -hybridised nitrogen linked to phosphorus. " Various acyclic bis(aminophosphines) have also been reported, including the imino-functional system (96), the bis(phosphino)-hydrazines (97) and -ureas (98), and the l,8-bis[bis(dialkylamino)phosphino]naphthalenes (99). There has also been significant activity in the synthesis of cyclic aminophosphines. An improved route to the four-membered ring system (100) is afforded by the reaction of phosphorus trichloride with t-butylamine in a 1 3 mole ratio in THF. Treatment of this with ammonia in THF/triethylamine at — 78°C gives (101),... 

Kellogg and Feringa have conducted extensive work on cyclic bis-urea molecules derived from fran5-l,2-diaminocyclohexane and 1,2-diaminoben-zene. In particular they studied aliphatic, aromatic and ester derivatives and demonstrated that some of these molecules gel organic solvents below 1 w/v%. 

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