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

Abstract

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 I2 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‐RP and 2‐Sp 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 nBu derivative 2b to 3b, i.e., ΔH‡ = 21.3 kcal mol–1, ΔS‡ = –9.4 eu. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis and crystal structure of 5-carbaphosphatranes containing a four-membered cycle

“…Akiba. [11][12][13][14][15][16][17][18] To † 3,3,10,10-Tetrakis(trifluoromethyl)-1-phenyl-6,7-benzo-2,4,8,9-tetraoxa-1-phosphatricyclo[3.3.2.0 1,5 ]decene 5. Hexafluoroacetone (4.2 g, 0.25 mol) was condensed to the mixture of phosphonite 3 (4.88 g, 0.012 mol) and CH 2 Cl 2 (30 ml) in a dry argon atmosphere at -45°C.…”

Chiral Hypervalent, Pentacoordinated Phosphoranes

“…The effects of substituents in the monodentate aryl ring of O-cis arylphosphoranes on the stereomutation process, along with a kinetic study on the stereomutation of O-cis 66k-n to O-trans 67k-n were studied in details. The exclusive generation of O-cis 66 could be observed for the alkyl derivatives 66a-c right after oxidation, however, in the case of the phenyl derivative 66d the O-cis Later on, Akiba and co-workers reported the first example of an "anti-apicophilic" (O-cis) spirophosphoranes 67 [79][80][81], in which the oxygen atom occupies an equatorial position and the carbon atom is located in an apical position of a five membered ring, which is in contrast to the general concept of apicophilicity. According to the procedure shown in Scheme 29 (O-cis) phosphoranes 66 were obtained.…”

“…Its cyclization, initiated by the nucleophilic attack of the alkoxide anion at the phosphorous centre and the simultaneous extrusion of I − produced O-cis-alkyl-or aryl spirophosphoranes 66. Later on, Akiba and co-workers reported the first example of an "anti-apicophilic" (O-cis) spirophosphoranes 67 [79][80][81], in which the oxygen atom occupies an equatorial position and the carbon atom is located in an apical position of a five membered ring, which is in contrast to the general concept of apicophilicity. According to the procedure shown in Scheme 29 (O-cis) phosphoranes 66 were obtained.…”

Reaction of 5-oxo-2-phenyl-4,4-bis(trifluoromethyl)-4,5-dihydro-1,3,2-benzodioxaphosphepine with chloral. The synthesis and spatial structure of 5-carbaphosphatrane containing a four-membered ring

“…That is why their synthesis, reactivi ties, and configurational stabilities are under intensive study. [1][2][3][4][5][6][7][8][9][10][11][12] The benzodioxaphosphole fragment stabilizes the pentacoordinated state of phosphorus most efficient ly. 5 Taking this into account, we have proposed a new approach to the preparation of phosphoranes that involves reactions of activated carbonyl compounds with benzo dioxaphospholes containing the tricoordinated P atom and a carbonyl or imino group in the γ or δ position relative to the P atom in the endocyclic substituent.…”