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A New Method for the Formation of Anti‐apicophilic ( O ‐ cis ) Spirophosphoranes – Kinetic Studies on the Stereomutation of O ‐ cis Arylspirophosphoranes to Their O‐trans Isomers
Author(s) -
Kajiyama Kazumasa,
Yoshimune Miki,
Kojima Satoshi,
Akiba Kinya
Publication year - 2006
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/ejoc.200600031
Subject(s) - pseudorotation , chemistry , derivative (finance) , enantiomer , stereochemistry , reagent , medicinal chemistry , ring (chemistry) , organic chemistry , financial economics , economics
P–H spirophosphorane 4 bearing two Martin ligands was converted to dianions ( 5a – n ), bearing R groups, with excess organolithium reagents (RLi). Subsequent oxidation with I 2 at ambient temperature gave anti ‐apicophilic ( O ‐ cis ) spirophosphoranes 2a – n . All anti ‐apicophilic phosphoranes 2a – n isomerized irreversibly to the O ‐ trans spirophosphoranes 3a – n , respectively. For 2,6‐dialkylphenyl derivatives 2k – n , the barrier for pseudorotation between enantiomers 2 ‐ R P and 2 ‐ S p was rather high, and thus the interconversion could not be observed on the NMR timescale. The activation parameters for the pseudorotation of the triisopropylphenyl (TIP) derivative 2n to 3n were almost identical with those of n Bu derivative 2b to 3b , i.e., Δ H ‡ = 21.3 kcal mol –1 , Δ S ‡ = –9.4 eu. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)