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An efficient approach to functionalized 4,6-disubstituted-and 4,6,6-trisubstituted-1,3-oxazinan-2-ones skeleton has been developed through the reaction of semicyclic N, O-acetals 4a and 4b with 1,1-disubstituted ethylenes 5 or 8. As a result of such a [4 + 2] cycloaddition process, 4,6,6-trisubstituted-1,3-oxazinan-2-ones 6aa, 6af-6au, 7ba, 7bf-7bw and 6,6-spiro containing 1,3-oxazinan-2-ones 9ad, 9ae, 10ba-10bg were obtained in 36%-96% yields and with moderate to excellent diastereoselectivities. In addition, the synthesis of (±)-norallosedamine 12 could be conveniently achieved from the cycloadduct 7bf.

A novel approach to skipped dienes has been developed through the TMSOTf-mediated one-pot addition–substitution of olefins 2a, 2f and 2g with imines 1a–1g, and a series of aryl substituted skipped dienes 3aa–3gf were accordingly obtained in 62%–94% yields. Moreover, semicyclic N,O-acetals 5 and 7 could also undergo this transformation to produce the corresponding skipped dienes 6aa and 6af–6al and 8ba and 8bf–8bk in moderate to good yields.

The Cu(OTf)2 catalyzed Ugi-type reactions of N,O-acetals with isocyanides have been described for the synthesis of pyrrolidinyl and piperidinyl 2-carboxamides. 4-Hydroxy-5-substituted-prolinamides can be obtained in high diastereoselectivities (2,4-cis/trans > 19 : 1) and a stereoselective model was proposed for 2,4-cis selectivity. Moreover, 4-F-VH 032, a novel analog of the VHL ligand, was conveniently obtained by utilizing the present method.

A novel approach to skipped dienes has been developed through the TMSOTf-mediated one-pot addition-substitution of olefins 2a, 2f and 2g with imines 1a-1g, and a series of aryl substituted skipped dienes 3aa-3gf were accordingly obtained in 62%-94% yields. Moreover, semicyclic

The Cu(OTf)