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4 Polish Journal of Chemistry

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Synthessi of 3-Benzyl-1,3-thiazolidines by {2+3}-Cycloaddition of Sonochemically Generated Azomethine Ylides with Thiocarbonyl Compounds

100%

Gebert A. , Linden A. , Mlostoń G. , Heimgartner H.

tom Vol. 77 / nr 7

867-879

Sonification of N-benzyl-N-(methoxymethyl)-N-[(trimethylsilyl)methyl]amine (5a) in the presence of LiF led to the formation of the reactive azomethine ylide 1d, which was intercepted by cyclic thioketones to give spirocyclic 1,3-thiazolidines. In the case of 2,2,4,4-tetramethylcyclobutane-1,3-dithione (13), the 1:1- and 1:2-cycloadduct, respectively, was formed as the major product depending on the ratio of the starting materials. With 1,3-thiazole-5(4H)-thiones, 1d undergoes stereoselective [2+3]-cycloadditions with the C=S group to yield spirocyclic 1:1-adducts. In the case of the 1,3-dipole generated from N-benzyl-N-(methoxymethyl)-N-[1-(trimethylsilyl)ethyl]amine (5b), the [2+3]-cycloaddition proceeded in a non-regioselective manner leading to a mixture of regio- and diastereoisomers.

Synthesis of Iminosugars from alfa,beta-Unsaturated Lactones and N-Benzyl Nitrone

100%

Panfil I. , Urbańczyk-Lipkowska Z. , Chmielewski M.

2005

tom Vol. 79 / nr 2

239-249

1,3-Dipolar cycloadditions of N-benzyl nitrone 12 to D-glycero _-lactone 13 and to D-threo _-lactone 14 proceed with excellent stereoselectivity to provide only one adduct in each case, 16 and 17, respectively. The same reaction performed with L-erythro _-lactone 15 afforded two stereoisomers 18 and 19 in the ratio ca. 2.5:1. Cycloadducts 16-19 were subsequently subjected to a sequence of reactions involving hydrogenolysis of the N-O bond and intramolecular alkylation of the nitrogen atom by C-4 or C-5 carbon atom of the sugar backbone to afford 1,2-dideoxy iminosugars 25, 31, 38, 44 and 50 with a protected hydroxymethyl group at C-2 carbon atom.

Synthesis of N-Unsubstituted 1,3-Thiazollidines by [2+3]-Cycloaddition of an Azomethine Ylide with Thiocarbonyl Compounds

88%

Gebert A. , Linden A. , Mlostoń G. , Heimgartner H.

tom Vol. 77 / nr 2

157-167

1,3-Dipolar cycloadditions of azomethine ylides with thiocarbonyl compounds have been used for the preparation of N-unsubstituted 1,3-thiazolidines. The reactive 1- phenyl-N-(trimethylsilyl)azomethine ylide (1c) was generated in situ by treatment of N-(benzylidene)[(trimethylsilyl)methyl]amine (6) with trimethylsilyl triflate and CsF in HMPA. All cycloadditions proceeded non-regioselectively, which led to mixtures of 4-phenyl- and 2-phenyl-substituted 1,3-thiazolidines.

Synthesis and Structure of Spirocyclic Tetrahydrothiophene Derivatives Bearing a 'Cage' Residue

75%

Romański J. , Mlostoń G. , Linden A. , Heimgartner H.

2005

tom Vol. 79 / nr 6

973-979

Trapping of the thiocarbonyl S-methanide 4 with tetracyanoethene and N-methylmaleimide led to the [3+2]-cycloadducts 11 and 12, respectively. The structures of these cycloadducts were established by X-ray crystallography. The 1,3-dipole 4 has been generated by thermal decomposition of the corresponding 2,5-dihydro-1,3,4-thiadiazole 2, which was prepared by the 1,3-dipolar cycloaddition of diazomethane with thioketone 1.