Imidazolidinone salts

Dissymmetric ferrocenyldiphosphines have been synthesized from (R)-(+)-N, N -dimethylaminoethylferrocene. The diphosphines have been used as ligands in asymmetric transfer hydrogenation of acetophenone in the presence of ruthenium catalysts.297 Asymmetric transfer hydrogenation of a,/S-unsaturated aldehydes with Hantzsch dihydropyridines and a catalytic amount of MacMillan imidazolidinone salt (12) leads to the saturated carbonyl compounds in high yields and excellent chemo-and enantio-selectivities.298 ... 

General Procedure for the Intramolecular Michael Addition with Chiral Imidazolidinone Salt [33] (p. 90)... 

The imidazolidinone salt (5.110) has also been used as a catalyst in the asymmetric chlorination of aldehydes. For example, octanal (5.112) is converted into the a-chloroaldehyde with high ee using the antipode of (5.110) and quinone (5.113) as the chlorine source. Jorgensen and coworkers have achieved similar levels of enantioselectivity in this transformation using C2-symmetric diphenylpyrrolidine (5.114) as the organocatalyst in combination with NCS. ... 

MacMillan s imidazolidinone salts, used successfully in the organocatalysed Diels-Alder reaction (see Section 8.1) also function as effective catalysts in the asymmetric nitrone cycloaddition with simple monodentate dipolarophiles. Thus acrolein (8.63) and crotonaldehyde (8.99) both react with acyclic C-aryl, N-benzyl nitrones and C-aryl N-alkyl nitrones such as (8.198) with high ees ranging from 90 to 99% in the presence of the perchlorate salt of imidazolidinone (8.91). 

The asymmetric Diels-Alder reaction of a,(3-unsaturated ketones have met much less success, most likely due to the lower reactivity of ketones in iminium ion formation compared to the corresponding 2-enals. This setback was overcome by MacMillan in 2002 when they extended the scope of their Diels-Alder protocol to include a,(3-unsaturated ketones using the more reactive imidazolidinone salt 16 as... 

A review of recent developments in 1,3-dipolar cycloaddition of nitrones with sila-, thia-, phospha-, and halo-substituted alkenes has been reported. A DFT study of solvent effects on the intermolecular 3-l-2-cycloaddition reaction of norbornadiene with 3,4-dihydroisoquinoline A(-oxide at 398.15 K indicated that the reaction proceeds via a synchronous concerted mechanism. Chiral imidazolidinone salts, in the absence of water, promote the 1,3-dipolar cycloaddition reaction of alanine-derived ketonitrones... 

C3H4N2 288-32-4) see Bifonazole Butoconazole Clotrimazole Eprosartan Fenticonazole Isoconazole Ketoconazole Miconazole Neticonazole hydrochloride Omoconazole nitrate Oxiconazole Ozagrel 1/f-imidazole lithium salt (C,H3LiN2 55986-39-5) see Flutrimazole 2-imidazolidinone... 

Nucleophilic attack of substituted alkylamines including benzylamines to 6,7-dihydro-imidazo[l,2- ]imidazole-2,5-diones 34, cleaved the imidazolidinone ring to generate the acetamide derivatives 81 (Equation 34) <1998APH389, 2001JST73>. Reaction of the tricyclic thiazolium salt 45 with methoxylamine gave the oxime 82 (Equation 35) <1999JME2828>. 

The MacMillan group has also shown that cycloaddition reactions (see also Chapter 8) can be performed highly diastereo- and enantioselectively. The [3+2]-cycloaddition of nitrones and a,/i-un saturated carbonyl compounds in the presence of 20 mol% of a phenylalanine-derived imidazolidinone acid salt led to products with 99% ee [32]. An example of an enantioselective rearrangement reaction (see also Section 13.6) with 99% ee has been reported by the Fu group [33], who used 2 mol% of a planar chiral DMAP derivative as catalyst. 

A solution of 5.0 g of l-(m-chlorophenyl)-2-imidazolidinone in 30 ml of dimethylformamide is added at room temperature to a mixture of 1.5 g of 50% NaH (mineral oil emulsion) in 30 ml of dimethylformamide. The reaction mixture is stirred for 1 h at room temperature and then 4.5 g of 3,3-dimethyl-l-(2-chloroethyl)azetidine are added. The mixture is stirred again at room temperature for 2 h and then it is heated for 5 h at 80°-85°C. The salts are filtered off and the solvent is removed under vacuum. The residue is taken up with 8 ml of 18% HCI and 16 ml of water and extracted with diethyl ether. 

Scheme 2.33 Direct enantioselective a-fluorination of aldehydes catalyzed by (S)-2-[bis(3,5-bistrifluoro-methylphenyl)trimethyl-silanyloxymethyljpyrrolidine 3b and the salt of imidazolidinone compound 3g.

The direct enantioselective a-chlorination of aldehydes leads to important intermediates 27 in organic synthesis (Scheme 2.34). This reaction was developed independently by two groups MacMillan et al. applied the salt of the imidazolidinone 3g as the catalyst, as i-proline was found to be a poor catalyst for this reaction (Scheme 2.34) [26a]. Various chlorinating reagents were tested, and the per-chlorinated quinone 28 was found to provide the best enantioselectivity. It was... 

Alkynylsilanes can be converted into alkynylcoppers by treatment with Cu salts in an aprotic polar solvent such as l,3-dimethyl-2-imidazolidinone (DMI).62 The Cu-promoted coupling reactions via the Si-Cu transmetallation of alkynylsilanes are valuable for the syntheses of alkynyl ketones, 1,3-diynes, 1,3-enynes, and 1-aryl-l-alkynes from acid chlorides,62 alkynyl chlorides,63 alkenyl iodides,64 and aryl iodides,64 respectively (Equation (12)). In addition, symmetric 1,3-diynes can be prepared by the CuCl-mediated homocoupling of alkynylsilanes.65 653... 

An example of an asymmetric catalytic version was also presented in our first publication. This protocol was subsequently optimized and we developed a highly enantioselective variant using the trichloroac-etate salt of MacMillan s second generation imidazolidinone (19) as the... 

Preparative Methods the commercial glycine Wmethylamide hydrochloride is converted to the racemic imidazolidinone (2) by imine formation with Pivalaldehyde and cyclization under acidic conditions (eq 1). The mandelate salt of like configuration is less soluble and is used for highly efficient resolution subsequent treatment with Boc anhydride (Di-t-butyl Dicarbonate) gives the enantiomeric Boc-BMI (1) (eq 2). 

The first enantioselective organocatalytic 1,3-dipolar cycloaddition of acyclic nitrones with acrolein and crotonal-dehyde has been reported <2000JA9874>. In particular, the reversible formation of iminium ions from a,/3-unsatu-rated aldehydes and the enantiopure imidazolidinone 535 provided ( A-4-formylisoxazolidines in high yields and ees (Equation 86). A polymer-supported version of catalyst 535 was also prepared <2004EJ0567>. The catalytic performance of various chiral pyrrolidinium salts in the cycloaddition of 1-cycloalkene-l-carboxaldehydes was also evaluated <2003EJO2782>. 

Analogous alkylations with unsaturated ketones can also be effected with silica-supported benzenesul-fonic acid sodium salt or, with some stereoselectivity, using a chiral imidazolidinone organo-catalyst. Optical induction can also be achieved in the addition of indole to alkyhdene malonates using bisoxazoline copper(II) complexes. ... 

Copper(II) salts are efficient one-electron oxidants for the generation of radicals from lithium enolates [1]. This concept was successfully applied for the oxidative coupling of ketones or amides 36 to afford the corresponding 1,4-dicarbonyl compounds 37 in good yield [17]. If an optically active imidazolidinone is used as chiral auxiliary, the reaction exhibits an excellent simple and induced diastereoselectivity (Scheme 12). 

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