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Reversal of Diastereoselectivity of Mesitonitrile Oxide 1,3-Dipolar Cycloadditions with Penta-1,4-diene-3-ol by Mg(II)

Micuch P., Fisera E., Cyrański M.

Polish Journal of Chemistry

2005

Vol. 79 / nr 1

65-72

1,3-Dipolar cycloadditions of mesitonitrile oxide (4) to penta-1,4-diene-3-ol (5) proceed regioselectively irrespective of the presence or absence of the Mg(II) additive. Addition of Grignard reagent reverses the diastereoselectivity of the cycloaddition. The reaction of mesitonitrile oxide with magnesium alkoxide of penta-1,4-diene-3-ol (5) proceeded with exclusive diastereoselectivity giving the syn 6b and 7c isomer of the resulting isoxazolines.

Application of Dialkyltin Hydrides Containing the Chiral 2-(4-Isopropyl-2-oxazolinyl)-5-phenyl Ligand in Radical Cyclizations at the Steady State

Pianowski Z., Staliński K.

Polish Journal of Chemistry

2005

Vol. 79 / nr 4

721-729

New N-coordinated dimethyl and di-n-butyl tin hydrides containing the oxazole moiety appeared to be useful in radical cyclizations of acyclic dihalides at the steady state. Both the hydrides were prepared in three steps starting from (-)-(S)-(2-bromophenyl)- 4-isopropyl-4,5-dihydrooxazole. The advantages of the hydrides are at least twofold. First, a resolution of the radical intermediates allows generating higher stereomeric excess than in the case of commercially available hydrides. Second, tin by-products are easily removed.

Highly Diastereoselective Addition of Grignard Reagents to N-Glyoxyloyl-(2R0-bornane-10,2-sultam-Comparative Studies

Raszplewicz K., Sikorska L., Kiegiel K., Jurczak J.

Polish Journal of Chemistry

2002

Vol. 76 / nr 11

1595-1600

N-Glyoxyloyl-(2R)-bornane-10,2-sultam (3), readily prepared from (2R)-bornane-10,2- sultam (1), was used in the Grignard reaction with methylmagnesium bromide (4a), phenylmagnesium chloride (4b), benzylmagnesium chloride (4c), allylmagnesium chloride (4d), and vinylmagnesium bromide (4e). Reactions of 3 with Grignard reagents 4a-d led to the desired adducts 5 with predominance of the (14S)-diastereoisomer. The reaction of 3 with vinylmagnesium bromide (4e) failed to give the adduct of type 5. Stereochemical models for the reactions studied are proposed.