Butenolide. vinylogous addition

A direct vinylogous addition of deconjugated butenolide to enals can be catalysed by aminal-pyrrolidine (153) at 15mol% loading in toluene at room temperature with... 

A ry -selective, organocatalytic, enantioselective vinylogous Mukaiyama-Michael addition of 2-trimethylsilyloxyfuran to a,/ -unsaturated aldehydes to produce 7-butenolides was achieved by using a chiral amine catalyst... 

Vinylogous Mukaiyama-Michael additions of 2-trimethylsilyloxyfuran to 3-alkenoyl-2-oxazolidinones to provide 7-butenolides were shown to be /7-selective. The reaction could be rendered enantioselective in the presence of a (T symmetric copper-bisoxazoline complex <1997T17015, 1997SL568> or a l,T-binaphthyl-2,2 -diamine-nickel(ii) complex as catalyst, as depicted in Equation (16) <2004CC1414>. 

The vinylogous Mannich reaction of 2 silyloxy furans and imines may also be catalyzed through chiral Brpnsted acids, as shown by Akiyama et al. [10]. Previously, Akiyama [11] and Terada [12] had independently discovered that 3,3 substituted BINOL based phosphoric acids were excellent Bronsted acids for a broad range of mainly imine addition reactions via protonation of the imines and in situ formation of chiral iminium contact ion pairs. Using the slightly modified phosphoric acid 28 as catalyst carrying additional iodine substituents in the 6,6 positions, the y amino substituted butenolides 27 were obtained in excellent enantioselectivity and variable diastereoselectivity (Table 5.4). 

New Au(III)-pyridine-2-carboxylate complexes were developed to catalyze the intramolecular reaction between furan and acetylene to form phenols <04AE(G)6545>. These pre-catalysts provide higher reaction conversion than AuClj. The Lewis acid catalyzed vinylogous Mukaiyama-Mannich addition of trimethylsilyloxyfuran to aldimines, that generates 6-amino-Y-butenolide intermediates, was applied to the synthesis of piperidines... 

Li and co-workers [129] developed the first enantioselective organocatalytic direct vinylogous Michael addition of y-butenolides 130 to chalcones catalyzed by the vicinal primary-diamine salt 56 (Scheme 5.64). The reaction proceeded smoothly to afford the highly valuable chiral y-butenolides 131 with good yields and high... 

SCHEME 5.64. Direct vinylogous Michael addition of y-butenolides to enones. 

Most recently, Terada and co-workers [132] realized the first organocatalytic asymmetric direct vinylogous Michael addition of a-tert-butylthio-substituted furanones to nitroalkenes. The reaction was catalyzed by axially chiral guanidine 133, leading to densely functionalized y-butenolides 130a in high iy/j-diastereo- and enantioselectivities. However, no example has showed for the unsubstituted -y-butenolide (Scheme 5.65). 

The asymmetric vinylogous Michael addition of y-butenolide(buteno-4-lactone) to RCH=CHCH=0 has been reported to proceed with high enantioselectivity and moderate diastereoselectivity in the presence of the Jprgensen-Hayashi catalyst (123a) and AcOLi.236... 

The enantioselective vinylogous Mukaiyama—Michael addition of 2-silyloxyfurans to cyclic unsaturated oxo esters afforded a variety of compounds bearing a y-butenolide or y-lactone connected to a cycloalkane or cycloalkene moiety (13JOC2289). The reaction of siloxyfurans with aromatic aldimines could be catalyzed efficiently by silver(I) complexes of the Ar-BlNMOL-derived chiral monophosphine (13T8777). 

The direct vinylogous aldol additions of a,j0-dichloro-y-butenolides and -butyro-lactams have been examined computationally, seeking to identify the origin of the observed diastereoselectivities and especially the reversal observed between the two systems.In addition, reactions with ort/io-substituted benzaldehydes have been 0 compared with those with benzaldehyde itself. 

Demethylated quinine (327) was employed as a catalyst for the vinylogous Michael addition of /-substituted budenolides to 3-aroyl acrylates ArC0CH=CHC02R and 1,2-diaroylethylenes ArCOCH=CHCOAT to produce /,/-disubstituted butenolides (328) and (329) with <99% ee and >99 1 drP ... 

A review, see X. Jusseau, L. Chabaud, C. Guillou, Synthesis of y-butenolides and a, 3-unsaturated y-butyrolactams by addition of vinylogous nucleophiles to Michael acceptors. Tetrahedron 70 (2014) 2595-2615. 

A. Quintard, A. Lefranc, A. Alexakis, Highly enantioselective direct vinylogous Michael addition of y-butenolide to enals, Org. Lett. 13 (2011) 1540-1543. 

J. Wang, C. Qi, Z. Ge, T. Cheng, R. li. Efficient direct asymmetric vinylogous Michael addition reactions of y-butenolides to chalcones catalyzed by vicinal primary-diamine salts, Chem. Commun. 46 (2010) 2124-2126. 

M.S. Manna, V. Kumar, S. Mukherjee, Catalytic enantioselective construction of quaternary stereocenters by direct vinylogous Michael addition of decoi ugated butenolides to nitroolefins, Chem. Commun. 48 (2012) 5193-5195. 

Under the catalysis of 22c, a structurally similar pro-nucleophile, a-tert-butylthio-substituted furanone, underwent the highly syn- and enantioselective vinylogous Michael addition to nitroalkenes (Scheme 7.38) [62). These methods allowed fadle access to optically active polyfunctionaUzed butenolides, which are versatile chiral synthons in organic synthesis. 

Thiourea (348) has been developed as an organocatalysts for the vinylogous Michael addition of non-conjugated butenolides (349) to maleimide (350) (R = Ph), which provided succinimides (351) with <18 1 dr and <99% eeP ... 

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