Nitroolefins 3-aryl

The reaction of the silyl enol ether with aryl nitroolefins in the presence of an excess of TiCl2(O Pr)2 and TADDOL-TiCl2, gave the cycloadducts, which upon... 

In the presence of 10 mol% of this catalyst, the malonates 56 could be added to several nitroolefins 57 with up to 93% ee. Apolar solvents such as toluene are crucial for high ee values. It is also noteworthy that (i) good ee can be achieved with catalyst 55 even in the absence of solvents, i.e. with a mixture of the neat starting materials 56 and 57, and that (ii) the range of Michael donors/acceptors includes aryl- and alkyl-substituted nitroolefins and 2-alkylated malonates. 

The diphenylprolinol silyl ether 45a catalyst was developed by the Hayashfs group for the addition of a-unbranched aldehydes to aryl and alkyl substituted nitroolefins [35]. This catalyst, as well as the perfluoroalkyl derivative 45b [36],... 

Jorgensen and co-workers employed chiral bis-sulfonamide catalyst 27, a proven ligand for metal-based asymmetric catalysis, for the Friedel-Crafts alkylations of N-methylindoles (24) using -substituted nitroolefins [52]. Using optimized conditions, 2 mol% 27 gave the desired indole alkylation products of substituted aryl and heteroaryl nitroolefins in moderate to high yields (20-91%) and moderate enantiopurities (13-63% ee Scheme 6.3). Aliphatic -substitution... 

With chiral diamine 24, in the form of a trifluoroacetate salt, the classic aqueous biphasic protocol has been successfully applied to the asymmetric Michael reaction of ketones with both aryl and alkyl nitroolefins. Brine is used as the aqueous phase. ... 

TBAF efficiently unmasks nucleophilic azide for C-N bond formation. TBAF stimulated the reaction of benzonitrile with TMSN3 to form 5-substituted IH-tetrazoles (eq 45). Under similar conditions, 4-aryl-lH-l,2,3-triazoles can be synthesized by TBAF-catalyzed cycloadditions of electron poor nitroolefins (eq46). 2 - 25... 

Nitroolefins combine with aminopyridines in the presence of a tetrabu-tylammonium iodide catalyst to form imidazo[l, 2-a]pyridines (Scheme 40). Steric hindrance in the form of a methyl group at C-6 on the aminopyridine decreased the reaction yield. The electron-withdrawing effects of chloride on the aminopyridine also slowed the reaction down. Ort/io-substituents on the aryl group of the nitro olefin also significandy decreased the reaction yield. The use of a heterocyclic substituted nitro olefin worked well in this reaction (14SL718). 

Michael adducts from p-aryl- and P-alkyl substituted nitroolefins in high yields (68-97%), good diastereoselectivities (dr 3/1 to >20/1), and excellent enantioselec-tivities (88-99% ee). This novel organocatalytic approach has been used in the formal synthesis of the alkaloid (-H)-physostigmine (Scheme 2.92). Catalyst 168 was... 

H-bond donor capability is also displayed by some cationic molecules such as the tetraminophosphonium 40 (Scheme 11.23). This type of the so-called chiral proton" catalysis [83] has been demonstrated by Ooi in the addition of aryl amines to nitroolefins [84]. The arylaminophosphonium barfate 40 was able to catalyze the aza-Michael addition to afford the corresponding adducts in excellent yields and enantioselectivities. The same group has extended the described protocol for the effective addition of aryl amines to propargyl-substituted nitroolefins [85]. 

A BINAP-derived bifunctional thiophosphoramide gives >98% del>99% ee in Michael addition of cyclohexanones to both aryl- and alkyl-substituted nitroolefins. Imidazolylmethyl ketones undergo one-pot Michael-aldol cascade reactions with Q ,/3-unsaturated aldehydes in DCM at 20 °C using the simple organocatalyst, prolinol... 

Dihydroisoquinoline esters undergo an oxidative [3 + 2] cycloaddition with nitroolefines or N-sulfuryl aldimines when treated with a cobalt catalyst (Scheme 69) (130BC6691). This cycloaddition provides a fairly robust approach to dihydropyrrolo[l,2-rj]isoquinolines. Nitroolefins with a number of aryl substituents underwent reaction with the dihydroiso-quinolines.The aryl groups could have either electron-donating (methoxy)... 

A facile access to A-sulfonylimidates and their synthetic utility for the transformation to amidines and amides, (b) E. J. Yoo, S. H. Park, S. H. Lee, S. Chang, Org. Lett. 2009, 11, 1155-1158. A new entry of copper-catalyzed four-component reaction facile access to a-aryl P-hydroxy imidates. (c) R. Husmann, Y. S. Na, C. Bohn, S. Chang, Chem. Commun. 2010, 46, 5494—5496. Copper-catalyzed one-pot synthesis of a-functionalized imidates. (d) W. Song, W. Lu, J. Wang, P. Lu, Y. Wang, J. Org. Chem. 2010, 75, 3481-3483. A facile route to y-nitro imidates via four-component reaction of alkynes with sulfonyl azides, alcohols, and nitroolefins. (e) G. Murugavel, T. Punniyamurthy, Org. Lett. 2013, 15, 3828—3831. Novel copper-catalyzed multicomponent cascade synthesis of iminocoumarin aryl methyl ethers. 

The FeCl3-catalysed 3 -I- 2-cycloaddition of nitroolefins and IV-aryl benzamidines produced multi-substituted imidazoles in good yields. ... 

---