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Reaction of 1,2-Di(1-adamantyl)-2-thioxoethanone with Diazomethanes; 1,3- versus 1,5-Dipolar Electrocyclization of a Sterically Crowded Thiocarbonyl S-Methylide

100%

Mlostoń G. , Urbaniak K. , Nomura T. , Nakayama J. , Heimgartner H.

Polish Journal of Chemistry

2009

tom Vol. 83, nr 11

1945-1951

The reaction of 1,2-di(1-adamantyl)-2-thioxoethanone (4c) with diazomethane and 2-diazopropane yielded 2-acylthiiranes 6a and 6b, respectively, and no 1,3-oxathioles of type 7 were formed. The reaction course is explained via [2+3]-cycloaddition, elimination of N2, and 1,3-dipolar electrocyclization of the in ter me di ate acyl-substituted thiocarbonyl ylides of type 1. The fail ure of the competitive 1,5-dipolar electrocyclization is a result of the sterically unfavor able conformation 1a.

Reactions of Aza-ortho-xylylenes Generated from 3-Aryl-2,1-benzisothiazoline 2,2-Dioxides

86%

Modrzejewska H. , Wojciechowski K.

Polish Journal of Chemistry

2006

tom Vol. 80, nr 10

1695-1702

3-Methyl-3-(4-nitrophenyl)-2,1-benzisothiazoline 2,2-dioxides 1a,b undergo thermal extrusion (180°C) of SO2 to form aza-ortho-xylylenes, which after [1,5]-hydrogen shift give 1,1-diarylethylenes 9a,b. The corresponding 3-(nitropyridinyl) benzosultams undergo transformation into dihydro-azepino[2,3-b]indole derivatives 17.

Semiempirical Calculations in a Search for a Mechanism of 2-Methyl-4-phenylquinoline Formation from 4,4-Diphenyl-3-buten-2-one Oxime Acetate

86%

Suwiński J. , Mohamed M. A. A.

Polish Journal of Chemistry

2001

tom Vol. 75, nr 7

965-974

The known thermal non-catalytic formation of 2-methyl-4-phenylquinoline from 4,4- diphenyl-3-buten-2-one oxime acetate was analyzed by semiempirical MNDO, AM1 and PM3 methods of calculation, assuming the process consists of three steps: thermal disrotatory electrocyclization of the oxime acetate, inversion of the cyclic intermediate on the nitrogen atom and elimination of acetic acid from the inverted intermediate according to Ei mechanism. It appears from PM3 calculations, which led to better results than MNDO or AM1, that the disrotatory electrocyclization is the rate-determining step for the whole synthesis.