445398-86-7Relevant academic research and scientific papers
1,2-Dioxines containing tethered hydroxyl functionality as convenient precursors for pyran syntheses
Avery, Thomas D.,Caiazza, Daniela,Culbert, Julie A.,Taylor, Dennis K.,Tiekink, Edward R. T.
, p. 8344 - 8351 (2005)
A new method for the construction of tetrahydropyrans derived from readily available 1,2-dioxines containing a tethered hydroxyl moiety is described. The reaction proceeds via a base-catalyzed rearrangement of the 1,2-dioxines to either the isomeric cis or trans γ-hydroxy enones followed by intramolecular oxa-Michael addition of the tethered hydroxyl group.
Stereoselective organocatalytic oxidation of alcohols to enals: A homologation method to prepare polyenes
Chen, Xiaobei,Zhang, Yinan,Wan, Huixin,Wang, Wei,Zhang, Shilei
supporting information, p. 3532 - 3535 (2016/03/04)
A novel method for organocatalytic oxidation through oxidative enamine catalysis was developed with excellent compatibility for the direct syntheses of enals from simple saturated alcohols. By using this amine-catalyzed IBX-oxidation, a wide range of aromatic and aliphatic substituted enals were successfully generated in high yields and exclusively stereoselective E-geometry. Moreover, varying the solvents and/or the loading amounts of IBX allowed for the selective oxidation of alcohols and aldehydes. Importantly, the homologous application of this method provided a selective and efficient way of preparing various highly sensitive conjugated polyene frameworks, which are enriched in natural products.
Intramolecular Hydroamination/Cyclization of Conjugated Aminodienes Catalyzed by Organolanthanide Complexes. Scope, Diastereo- and Enantioselectivity, and Reaction Mechanism
Hong, Sukwon,Kawaoka, Amber M.,Marks, Tobin J.
, p. 15878 - 15892 (2007/10/03)
Organolanthanide complexes of the general type Cp′ 2LnCH(TMS)2 (Cp′ = η5-Me 5C5; Ln = La, Sm, Y; TMS = SiMe3) and CGCSmN(TMS)2 (CGC = Me2Si(η5-Me 4C5)(tBuN)) serve as effective precatalysts for the rapid, regioselective, and highly diastereoselective intramolecular hydroamination/cyclization of primary and secondary amines tethered to conjugated dienes. The rates of aminodiene cyclizations are significantly more rapid than those of the corresponding aminoalkenes. This dienyl group rate enhancement as well as substituent group (R) effects on turnover frequencies is consistent with proposed transition state electronic demands. Kinetic and mechanistic data parallel monosubstituted aminoalkene hydroamination/cyclization, with turnover-limiting C=C insertion into the Ln-N bond to presumably form an Ln-η3 allyl intermediate, followed by rapid protonolysis of the resulting Ln-C linkage. The rate law is first-order in [catalyst] and zero-order in [aminodiene]. However, depending on the particular substrate and catalyst combination, deviations from zero-order kinetic behavior reflect competitive product inhibition or self-inhibition by substrate. Lanthanide ionic radius effects and ancillary ligation effects on turnover frequencies suggest a sterically more demanding Ln-N insertion step than in aminoalkene cyclohydroamination, while a substantially more negative ΔS? implies a more highly organized transition state. Good to excellent diastereoselectivity is obtained in the synthesis of 2,5-trans-disubstituted pyrrolidines (80% de) and 2,6-cis-disubstituted piperidines (99% de). Formation of 2-(prop-1-enyl)piperidine using the chiral C1-symmetric precatalyst (S)-Me2Si(OHF)(CpR* )SmN(TMS)2 (OHF = η5-octahydrofluorenyl; Cp = η5-C5H3; R* = (-)-menthyl) proceeds with up to 71% ee. The highly stereoselective feature of aminodiene cyclization is demonstrated by concise syntheses of naturally occurring alkaloids, (±)-pinidine and (+)-coniine from simple diene precursors.
Highly stereoselective intramolecular hydroamination/cyclization of conjugated aminodienes catalyzed by organolanthanides
Hong, Sukwon,Marks, Tobin J.
, p. 7886 - 7887 (2007/10/03)
Efficient intramolecular hydroamination/cyclization of primary and secondary conjugated aminodienes can be effected by using organolanthanide precatalysts of the type Cp-2LnCH(TMS)2 (Cp- = η5-Me5C5; Ln = La, Sm, Y; TMS = SiMe3) and CGCSmN(TMS)2 (CGC = Me2Si(η5-Me4C5)(tBuN)). The transformation proceeds cleanly (≥ 90% conversion) at 25-60 °C with good rates and high regioselectivities, and with electronic effects leading to significant rate enhancements. Some features of the reaction parallel monosubstituted aminoalkene hydroamination/cyclization, including rate law (zero order in [aminodiene]), and rate enhancements observed with larger lanthanide ionic radii and/or more open catalyst ligation structures. Good to excellent diastereoselectivity is obtained in the synthesis of 2,5-trans-disubstituted pyrrolidines (80% de) and 2,6-cis-disubstituted piperidines (99% de) with using the corresponding α-methyl aminodiene precursors. Formation of 2-(prop-1-enyl)piperidine with the chiral C1-symmetric precatalyst (S)-Me2Si(OHF)(CpR*)SmN(TMS)2 (OHF = η5-octahydrofluorenyl; Cp = η5-C5H3; R* = (-)-menthyl) proceeds with up to 69% ee. Copyright
