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[2 + 3]‐Cycloadditions of Phosphonodithioformate S‐ Methanides with CS, NN, and CC Dipolarophiles
Author(s) -
Mlostoń Grzegorz,
Urbaniak Katarzyna,
Gulea Mihaela,
Masson Serge,
Linden Anthony,
Heimgartner Heinz
Publication year - 2005
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200590198
Subject(s) - chemistry , steric effects , fluorene , maleic anhydride , medicinal chemistry , structural isomer , yield (engineering) , regioselectivity , stereochemistry , organic chemistry , catalysis , copolymer , materials science , metallurgy , polymer
The reaction of the methyl (dialkoxyphosphinyl)‐dithioformates (= methyl dialkoxyphosphinecarbodithioate 1‐oxides) 10 with CH 2 N 2 at − 65° in THF yielded cycloadducts which eliminated N 2 between − 40 and − 35° to give the corresponding phosphonodithioformate S ‐methanides ( =methylenesulfonium (dialkoxyoxidophosphino)(methylthio)methylides) 11 ( Scheme 3 ). These reactive 1,3‐dipoles were intercepted by aromatic thioketones to yield 1,3‐dithiolanes. Whereas the reaction with thiobenzophenone ( 12b ) led to the sterically more congested isomers 15 regioselectively, a mixture of both regioisomers was obtained with 9 H ‐fluorene‐9‐thione ( 12a ). Trapping of 11 with phosphono‐ and sulfonodithioformates led exclusively to the sterically less hindered 1,3‐dithiolanes 16 and 18 , respectively ( Scheme 4 ). In addition, reactive CC dipolarophiles such as ethenetetracarbonitrile, maleic anhydride, and N ‐phenylmaleimide as well as the NN dipolarophile dimethyl diazenedicarboxylate were shown to be efficient interceptors of 11 ( Scheme 5 ).