53258-83-6Relevant academic research and scientific papers
Efficient Diastereoselective Syntheses of erythro- Or threo-a-Alkyl-β-hydroxy Sulfones by Reductions of α-Alkyl-β-keto Sulfones with TiCI4/BHg or LiEtsBH/CeCl3, Respectively
Marcantoni, Enrico,Cingolani, Simone,Bartoli, Giuseppe,Bosco, Marcella,Sambri, Letizia
, p. 3624 - 3630 (2007/10/03)
A stereoselective synthesis of erythro- and threo-α-alkyl-β-hydroxy sulfones by reduction of the corresponding α-alkyl-β-keto sulfones has been developed. The pivotal role in this methodology is played by the chelating or nonchelating properties of the Lewis acid employed. The strong chelating TiCl4 led to the erythro isomer in high diastereomeric excess in noncoordinating solvents (CH2Cl2) at -78 °C using BH3/py as reducing agent, while the nonchelating CeCl3 gave a high excess of the threo isomer in coordinating solvents (THF) at the same temperature using lithium triethylborohydride (LiEt3BH) as reducing agent. Moreover, this methodology has been successfully utilized for the synthesis of α-allyl-β-hydroxy sulfones, which are useful synthetic intermediates to obtain 2,5-disubstituted tetrahydrofurans by electrophilic cyclization.
ALKYATION STUDIES OF 5-EXO-METHYLENE SUBSTITUTED ISOXAZOLIDINES
Padwa, Albert,Carter, Stephen P.,Chiacchio, Ugo,Kline, Donald N.,Perumattam, John
, p. 2639 - 2646 (2007/10/02)
1,3-Dipolar cycloaddition of nitrones to phenylsulphonylallene gives in high yield and with complete regiospecificity 5-methyleneisoxazolidines.These on treatment with base and subsequent reaction with electrophiles afford both α- and γ-substituted products.With methyl iodide as the electrophile, only the α-methylated product was isolated.In contrast, reaction of the 5-exo-methylene-4-phenylsulphonylisoxazolidine with allyl bromide afforded the γ-allyated product.Formation of this was shown to be via direct γ-attack, rather than by α-attack, followed by a 3,3-sigmatropic rearrangement.Further studies show that the product ratio is controlled by a sensitive interplay between thermodynamic and steric factors and is very dependent on the nature of the electrophile used.
DIPOLAR CYCLOADDITION REACTION OF (PHENYLSULFONYL)PROPADIENE WITH NITRONES AND ALKYLATION STUDIES OF THE CYCLOADDUCTS
Padwa, Albert,Carter, Stephen P.,Chiacchio, Ugo,Kline, Donald N.
, p. 2683 - 2686 (2007/10/02)
Dipolar cycloaddition of nitrones with (phenylsulfonyl)propadiene give 4-sulfonyl substituted isoxazolidenes whose reactions with base and several electrophiles have been studied.
