Lewis acid-promoted carbonyl addition of 1,3-bis(silyl)propenes

Lewis Acid-Promoted Addition of 1,3-Bis(silyl)propenes to Aldehydes: A Route to 1,3-Dienes

“…Although we cannot offer an explanation to why the [1,3]-Brook rearrangement/1,4-elimination pathway is preferred, some additional support for this reaction manifold has been obtained (Scheme ). Reaction of ethyl glyoxalate ( 10 ) with bis(silane) 2a in the presence of SnCl 4 (0.3 equiv) afforded allylsilane 11 . Subjection of this material to a Lewis acid yielded solely ( E )-diene 12 , in agreement with the proposed mechanism.…”

Iridium-Catalyzed anti-Diastereo- and Enantioselective Carbonyl (Trimethylsilyl)allylation from the Alcohol or Aldehyde Oxidation Level

“…Again, good isolated yields were accompanied by exceptional levels of diastereo- and enantioselectivity. Thus, unlike corresponding protocols involving allylmetal reagents, − carbonyl (trimethylsilyl)allylation occured with equal facility from the alcohol or aldehyde oxidation level.…”

“…Here, using the isolated ortho -cyclometalated π-allyl iridium precatalyst derived from [Ir(cod)Cl] 2 , 4-cyano-3-nitrobenzoic acid, ( R )-SEGPHOS, and allyl acetate, we report that α-(trimethylsilyl)allyl acetate 1a couples to carbonyl compounds from the aldehyde or alcohol oxidation level, respectively, with exceptional levels of regio- and anti -diastereo- and enantioselectivity (Scheme ). In this fashion, α-(trimethylsilyl)allyl acetate serves as an alternative to previously reported silicon-containing 1,3- or 1,1-bimetallic allyl transfer agents. − As demonstrated in the case of adduct 4g , the products of (trimethylsilyl)allylation are readily converted to 1,4-ene-diols upon DMDO oxidation. , Additionally, conditions for proto-desilylation with allylic transposition have been identified in the absence of a hydroxyl protecting group. Finally, upon exposure to chlorosulfonyl isocyanate, formal [3 + 2] cycloaddition occurs to deliver γ-lactams possessing three contiguous stereogenic centers as single diastereomers.…”

A Mild and Efficient Method for Formation of C–N Bond from Benzyl Alcohols and Sulfonamide, Carboxamide, 4-Nitroanline and Azide Catalysed by SnCl4

“…SnCl 4 is an inexpensive Lewis acid and has been applied as the catalyst for the Ferrier rearrangement, 11 glycosylation reaction 12 and C-C bond construction. 13 Here we found SnCl 4 (10 mol% of the alcohol) in CH 2 Cl 2 could efficiently catalyse the direct substitution reaction between 1a and 2a to give 3a in 95% yield within 16 hours at room temperature (Entry 5 in Table 1). Moreover, BF 3 •OEt 2 could only catalyse this reaction with 77% yield which was less than the yield in the case of SnCl 4 (entry 6 in Table 1).…”

“…1,1'-Diphenylazidomethane (3h): The physical data shown below were comparable to those reported. 4 1 H NMR (400 MHz, CDCl 3 ) δ: 7.52-7.40 (m, 10H), 5.65 (s, 1H); 13…”