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Surprisingly Facile Addition of Thiols to the Double Bonds of Bicyclopropylidene and Other Methylenecyclopropanes
Author(s) -
Kozhushkov Sergei I.,
Brandl Melanie,
de Meijere Armin
Publication year - 1998
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199808)1998:8<1535::aid-ejoc1535>3.0.co;2-p
Subject(s) - chemistry , cyclopropane , markovnikov's rule , double bond , adduct , intramolecular force , ethanethiol , ring (chemistry) , medicinal chemistry , methylene , stereochemistry , thiol , catalysis , organic chemistry , regioselectivity
The addition of thiols 8a – h onto the double bonds of bicyclopropylidene ( 1 ) and methylenespiropentane ( 2 ) proceeds quantitatively in benzene at 20 to 75 °C in the absence of catalysts or radical initiators to give products 9 , 10 with complete retention of both three‐membered rings. Methylenespiropentane ( 2 ) yields exclusively the anti‐Markovnikov adduct 10 . The unsubstituted methylene‐cyclopropane ( 3 ) gives 9% of the ring‐opened compound 12 in addition to the anti‐Markovnikov adduct 11 . The addition of thiols to n ‐heptylbicyclopropylidene ( 13 ), methylenecyclopropylacetic acid ( 15 ), and the amino acids 17 , 19 containing bicyclopropylidene or methylenespiropentane fragments, does not proceed stereoselectively, though in all cases the mercapto function adds to the double bond with retention of the cyclopropane ring to give interesting new amino acids containing bicyclopropyl and spiropentyl fragments, respectively. The probable mechanism of this thiol addition is discussed in the light of a test with the cyclizing intramolecular addition of 2‐(2‐methylenecyclopropyl)ethanethiol 27 .