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Versatile Stereoselective Cycloadditions between Heterocumulenes and Phosphagermaallene Tip( t Bu)GeCPMes*: Experimental and Theoretical Investigations
Author(s) -
Ghereg Dumitru,
André Erwan,
Gornitzka Heinz,
Escudié Jean,
Ouhsaine Fatima,
Saffon Nathalie,
Miqueu Karinne,
Sotiropoulos JeanMarc
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201100281
Subject(s) - cycloaddition , chemistry , isothiocyanate , phenyl isothiocyanate , double bond , isocyanate , regioselectivity , medicinal chemistry , ring (chemistry) , stereochemistry , stereoselectivity , phenyl isocyanate , polymer chemistry , organic chemistry , catalysis , polyurethane
Phosphagermaallene Tip( t Bu)GeCPMes* 1 (Tip=2,4,6‐triisopropylphenyl, Mes*=2,4,6‐tri‐ tert ‐butylphenyl) reacts with phenyl isocyanate and tert ‐butyl isocyanate by a [2+2] cycloaddition that involves the GeC and CO double bonds to afford 1‐oxa‐2‐germacyclobutanes 2 and 3 . With N , N′ ‐dicyclohexylcarbodiimide, a [2+2] cycloaddition is observed between the GeC and CN unsaturations to lead to 1‐aza‐2‐germacyclobutane 6 with exocyclic PC and CN double bonds. In sharp contrast, 1 reacts with phenyl isothiocyanate, ethyl isothiocyanate, and carbon disulfide according to a [3+2] cycloaddition that involves the whole GeCP unit and the CS double bond to give transient phosphagermacarbenes (PGeHCs) 11 , 12 , and 13 . These new PGeHCs undergo CH insertions into one o ‐ t Bu group of Mes* (in the case of 11 and 12 ) or one o ‐ i Pr group of Tip (in the case of 13 ) with formation of tricyclic compounds 8 , 9 , and 10 , respectively. The reaction mechanisms that involve 1 and the phenyl isocyanate and the phenyl isothiocyanate are described and their regioselectivity is explained by theoretical calculations.