A,p-unsaturated y-butyrolactam

An efficient and diastereoselective synthesis of 5,6-dihydro-2H-pyran-2-acetates involves a Prins cyclization of acrylyl enol ethers mediated by TMSOTf.This strategy was used in the total synthesis of the natural compound (+)-civet (13JOC12182). Highly functionalized tricyclic dihydropy-ranopyrrolidin-2-ones are formed by a catalytic P,Y-selective Diels-Alder [4 + 2] annulation of a,P-unsaturated y-butyrolactams, in good yields and enantioselectivities (Scheme 8) (13AGE11329). 

In addition to 1,3-dicarbonyl compounds, a range of other nucleophiles has been successfully enantioselectively added to nitroalkenes. For example, Matsunaga and Shibasaki have used the vinylogous nucleophilicity of an a,p-unsaturated y-butyrolactam to develop its enantioselective Michael... 

The hybrid thiourea-cinchona alkaloid catalyst 14 proved to be effective in a stereoselective Michael addition reaction between a,p-unsaturated y-butyrolactam 11 and chalcone 12 (Scheme 3.22). The following mechanistic study addressed the issue of the origin of sfereoselecfion. 

Zhang, Y. Shao, Y.-L. Xu, H.-S. Wang, W. J. Organocatalytic Direct Asymmetric Vinylogous Michael Reaction of an a,P-Unsaturated y-Butyrolactam with Enones. Org. Chem. 2011,76,1472-1474. 

As shown in Fig. 8, the Ni2-lb complex was applicable to broad range of catalytic asymmetric reactions under simple proton transfer conditions [19-30]. As donors in direct Mannich-type reactions, not only a-nitroacetates, but also malonates, p-keto esters [22], p-keto phosphonates [23], and a-ketoaniUdes [24] gave excellent enantioselectivity and diastereoselectivity. It is noteworthy that the Ni2-lb complex also promoted vinylogous direct catalytic asymmetric Mannich-type reaction of an a,p-unsaturated y-butyrolactam, giving synthetically versatile functionalized a,p-unsaturated y-butyrolactam in 99% ee [25]. Because the Ni2-lb... 

Wang and coworkers reported high yields and enantioselectivity for the conjugate addition of a,P-unsaturated-Y-butyrolactam to chalcones (Scheme 6.31) as catalyzed 22 [73],... 

A vinylogous Michael addition of Q, j0-unsaturated y-butyrolactams (175) to a,p-unsaturated ketones has been shown to produce (176) (>30 1 dr, <99% ee) when catalysed by the triamine derivative (177). Catalysis by the cinchonine-derived thiourea (166b) afforded its diastereoisomer (>40 1 dr, <99% ee) ... 

The cyclisations and cycloadditions reported include the synthesis of benzofuranes from halophenols and alkynes,343 the generation of y-butyrolactams from chloroformamides,344 the intramolecular ring-closure to spirocyclic amides345 and the [3+2] cycloaddition of trimethylene methane precursors to a,p-unsaturated aldehydes,345 imines347 and activated alkenes (eq.33).348... 

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