76757-27-2Relevant academic research and scientific papers
γ-Silylated α,ss-unsaturated amides - Preparation by [1,5]-sigmatropic rearrangement and use as masked dienolate equivalents in carbonyl condensations
Green, James R.,Alo, Babajide I.,Majewski, Marek,Snieckus, Victor
experimental part, p. 745 - 759 (2009/12/04)
The reaction of lithium dienolates derived from N,N-dialkylsenecioamides (1a-1c) with triorganosilyl electrophiles occurs initially at the oxygen atom predominantly, and is followed by an O → C silicon migration to afford the γ-silylated senecioamides (4a-4h). The γ-silylated senecioamide Z-4a undergoes fluoride-ion-mediated condensations with aromatic aldehydes to give kinetic α-(6) and thermodynamic γ-(5) condensation product patterns comparable to lithium dienolates. The TiCl4-mediated reactions with aldehydes gives a-products (6) in a highly syn-selective manner. Possible transitionstate models for the syn-selective condensations are discussed and a chair-like transition state featuring bidentate coordination to titanium (11) is proposed.
γ-SILYLATED α,β-UNSATURATED AMIDES. FORMATION BY SILICON MIGRATION FROM O-SILYLATED VINYL KETENE AMINALS AND FLUORIDE- AND LEWIS ACID-MEDIATED ALDOL CONDENSATIONS
Green, J. R.,Majewski, M.,Alo, B. I.,Snieckus, V.
, p. 535 - 538 (2007/10/02)
O-Silylated vinyl ketene aminal 2, obtained from lithiated unsaturated amide 1, undergoes a thermal silicon migration to give γ-silylated product 3b which participates in fluoride- and titanium tetrachloride-mediated aldol condensations to give addu
Metalated Unsaturated Amides. Regio- and Stereoselective γ-Alkylation
Majewski, M.,Mpango, G. B.,Thomas, M. T.,Wu, A.,Snieckus, V.
, p. 2029 - 2045 (2007/10/02)
The reactions of lithiated and dilithiated unsaturated amides 4, 5, 12, 15, 18, 34, and 36 with a variety of electrophiles have been shown to produce deconjugated, α-alkylated products 6, 7, 13, 16, 19, 35, and 37, respectively, in good to excellent yields (Tables I, II, IV, and VI).Whereas lithiated 4 and dilithiated 5 do not undergo γ-alkylation, the corresponding species of 12 and 15, when converted to their cuprates by using cuprous iodide, afford γ products 4 and 17 with good regio- (67-90percent) and Z stereoselectivity (67-80percent) for E = allyl, prenyl, and geranyl.Differences between the reactions of cuprated, unsaturated amides and unsaturated carboxylic acids with nonallylic alkylating agents are discussed.The reaction of dicuprated N-methylsenecioamide (15) with prenyl bromide leads to a complex mixture of products which have been separated and characterized (Scheme III).The reaction of lithiated N,N-dimethylsenecioamide (18) with aromatic and pyridine aldehydes and some ketones has been shown to provide α (19) or γ (20) products, depending on the conditions of the reaction (Table VI).In this reaction, the reversible formation of the α product 19 and its conversion into the γ product 20 have been demonstrated (Scheme IV).The utility of the α- and γ-alkylated unsaturated amide products is illustrated by the syntheses of the monoterpenoid lavandulol (42) and the amide alkaloid piperlonguminine (43), respectively.
