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Precautionary Statements: P210u-P280a-P370+P378a-P403+P235-P501a

Pathak, R. B.; Dobson, B. C.; Ghosh, N.; Ageel, K. A.; Alshawish, M. R.; Saruengkhanphasit, R.; Coldham, I. Synthesis of the tricyclic core of manzamine A. Org. Biomol. Chem. 2015, 13 (11), 3331-3340.

; Wiley: New York, 1991; p 203.

must be prepared and transferred under inert gas (Ar or N) to exclude oxygen or moisture; solutions in THF are stable for weeks at -20 °C; at room temperature, 2-lithio-1,3-dithiane does not decompose via a carbenoid pathway, but abstracts a proton from the solvent. Handle in a fume hood.

; VCH: New York, 1989; pp 34, 721.

Antimicrobial activity of halogenated 3'-phenylspiro 3H-indole-3,2'-thiazolidine -2,4 (1H)-diones.

Based on this result, a six-membered chair like transition state was proposed to explain the resulting stereoselectivity (); this model is similar to that of the previous two asymmetric Umpolung reaction processes. Interestingly, the R configuration of the final product was in discordance to the stereochemistry of other enolate addition reactions that were studied before. This is the first example in which the (R,R)-1,2-cyclohexanediamine auxiliary resulted in the opposite control of forming chiral N-phosphonyl amine products. This observation is probably due to the fact that in nearly all previous asymmetric reactions, the lithium cation is coordinated unto the nitrogen of the N-phosphonyl amine reactant. However, in this reaction, the metal lithium is connected unto the oxygen atom of N-phosphonyl imine.

Chiral N-phosphonyl imines have been found to react with 2-lithio-1,3-dithiane, 2-lithio-2-methyl-1,3-dithiane and 2-lithio-2-phenyl-1,3-dithiane without the use of any Lewis acid promoters to produce α-amino 1,3-dithianes in good yields and good to excellent diastereoselectivities. The addition manner by which chiral N-phosphonyl imines are added into the solution of 2-lithio-1,3-dithiane was found to be crucial for this asymmetric Umpolung reaction. This reaction provide an easy access to α-amino-1,3-dithianes as versatile synthetic building blocks. The current synthesis was proven to follow the GAP chemistry (Group-Assistant-Purification chemistry) process by avoiding the use of traditional purifications via chromatography and recrystallization, i.e., the pure chiral α-amino-1,3-dithianes attached with the chiral N-phosphonyl group were readily obtained by washing the solid crude products with hexane or a mixture of hexane-ethyl acetate.

Biological activity of halogenated 2,3-diaryl-1,3-thiazolidin-4-ones.

3-methyl-2-(pentyl oxy) cyclopent-2-en-1-one

Alkylation of the anion provides a route to ɑ-keto acids (by dethioketalization with NBS), or to substituted acetic acids (by desulfurization): J. Org. Chem., 37, 505 (1972). For phase-transfer alkylation using allylic bromides, see: Liebigs Ann. Chem., 1589 (1982). With crotyl bromide, approx. 95% allylic rearrangement occurs.

Caracelli I, et al. Crystal structure of potassium trifluoro (2-methyl-1, 3-dithiano) borate, K (C5H9BF3S2).Kristallogr. - New Cryst. Struct.,2007,222,(3), 345-7.

1/2018-REC Medical Officer at the level of Senior Technical Officer (1)/Technical Gr.
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2,2'-Ethylenebis(1,3-Dithiane) For Synthesis

The lithiated derivative undergoes 1,4- (Michael) addition to a variety of ɑß-unsaturated compounds. However, the Mg derivative prepared by metallation with an alkylmagnesium halide gives an allylic alcohol by 1,2-addition: Chem. Ber., 114, 2924 (1981).

2,2'-Ethylenebis(1,3-Dithiane) For Synthesis, 10 g ..

Alkylation of the anion provides a route to ɑ-keto acids (by dethioketalization with NBS), or to substituted acetic acids (by desulfurization): J. Org. Chem., 37, 505 (1972). For phase-transfer alkylation using allylic bromides, see: Liebigs Ann. Chem., 1589 (1982). With crotyl bromide, approx. 95% allylic rearrangement occurs. The lithiated derivative undergoes 1,4- (Michael) addition to a variety of ɑß-unsaturated compounds. However, the Mg derivative prepared by metallation with an alkylmagnesium halide gives an allylic alcohol by 1,2-addition: Chem. Ber., 114, 2924 (1981). Pathak, R. B.; Dobson, B. C.; Ghosh, N.; Ageel, K. A.; Alshawish, M. R.; Saruengkhanphasit, R.; Coldham, I. Synthesis of the tricyclic core of manzamine A. Org. Biomol. Chem. 2015, 13 (11), 3331-3340.Gaggero, N.; Albanese, D. C. M.; Nava, D. A new approach to 4,6-disubstituted-3,4-dihydropyran-2-ones by Domino Michael addition-cyclization reaction under PTC conditions. Tetrahedron 2014, 70 (45), 8744-8749.

1,3-dithiane | C4H8S2 - ChemSynthesis

Gaggero, N.; Albanese, D. C. M.; Nava, D. A new approach to 4,6-disubstituted-3,4-dihydropyran-2-ones by Domino Michael addition-cyclization reaction under PTC conditions. Tetrahedron 2014, 70 (45), 8744-8749.

2-TRIMETHYLSILYL-1,3-DITHIANE | Gelest, Inc.

Caracelli I, et al. Crystal structure of potassium trifluoro (2-methyl-1, 3-dithiano) borate, K (C5H9BF3S2).Kristallogr. - New Cryst. Struct.,2007,222,(3), 345-7.Amos B Smith and Ming Xian. Anion relay chemistry: an effective tactic for diversity oriented synthesis.J Am Chem Soc.,2006,128,(1), 66-7. Acetyl anion equivalent, compare . It has been employed, for example, in the synthesis of methyl ketones: J. Org. Chem., 40, 231 (1975).

Generation and synthetic applications of 2-lithio-1,3-dithianes

A series of α-amino-1,3-dithianes have been synthesized via the asymmetric Umpolung reaction of 2-lithio-1,3-dithianes with chiral N-phosphonyl imines in good chemical yields (up to 82%) and good to excellent diastereoselectivities (>99:1). The addition manner by which chiral N-phosphonyl imines are slowly added into the solution of 2-lithio-1,3-dithiane was found to be crucial for achieving excellent diastereoselectivity. The current synthesis was proven to follow the GAP chemistry (Group-Assistant-Purification chemistry) process which avoids traditional purification techniques of chromatography or recrystallization, i.e., the pure chiral α-amino-1,3-dithianes attached with the chiral N-phosphonyl group were readily obtained by washing the solid crude products with hexane or the mixture of hexane-ethyl acetate.

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