Heteroatom‐Guided Torquoselective Olefination of α‐Oxy and α‐Amino Ketones via Ynolates

Abstract

Ynolates were found to react with alpha-alkoxy-, alpha-siloxy-, and alpha-aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the beta-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z selectivity is induced by orbital and steric interactions rather than by chelation. In a similar manner, alpha-dialkylamino ketones provided olefins with excellent Z selectivity. These products can be easily converted into multisubstituted butenolides and gamma-butyrolactams in good yield.

The effects of C–S and C–Se bonds on torquoselectivity: stereoselective olefination of α-thio and α-selenoketones with ynolates

“…2) could not be located as for the methoxy analogue. 9 Representative structures are shown in Figure 4, with their relative energies listed in Table 3. Since the structure of TSZ2 was quite similar to that of TSZ1, and those of TSE2 and TSE3 likewise similar to that of TSE1, except for the arrangements of the coordinating ether, TSZ2, TSE2, and TSE3 are not shown in this table (see Supplementary data).…”

“…In the course of this study, we have achieved a highly Z-selective olefination of a-alkoxy and a-aminoketones providing tetrasubstituted olefins where one carbon was inserted between the carbonyl group and the directing group, like the alkoxy group (Scheme 2). 9 In other words, the alkoxymethyl and aminomethyl groups rotate inward exclusively in the ring-opening of the oxetenes, while an alkoxy group rotates outward exclusively in the olefination of esters. 6 Initially we had considered the chelation control by the ethereal alkoxy and the amino groups as hard Lewis bases; however, the secondary orbital interactions turned out to be critical for the torquoselectivity rather than chelation.…”

Synthesis of Highly Substituted 3-Pyrrolin-2-ones from N,N-Disubstituted α-Amino Acids

“…Similar reactions as those proposed above are described in literature. The oxidative decarboxylation of N,N -disubstituted α-amino acids was, e.g., synthetically exploited by Weinstein and Craig; the condensation of enamines with oxalyl cloride − or with fumarates delivering 3-pyrrolin-2-ones has been published as well, and N -dealkylating ring closure finds its precedence. The combination of these reactions in a cascade, however, is new, and also new is the formation of 3-chloro-3-pyrrolin-2-one derivatives.…”

Structure–activity relationships of analogs of 3,4,5-trimethylfuran-2(5H)-one with germination inhibitory activities

“…They are, however, either multistep reactions, or provide 2 in low yield (Iwai et al, 1977;Sato et al, 1977;Shindo et al, 2006). Our syntheses of the presented analogs of the germination inhibitor 3,4,5-trimethyl-2(5H)-furanone (2) that possesses germination inhibitory activity as described by Light et al (2010), is based on the procedure recently published by Surmont et al (2010).…”