Takayuki Kawashima

A tetracoordinate 1,2-iodoxetane was prepared by the fluorination of a tricoordinate 1,2-iodoxetane with xenon difluoride followed by hydrolysis. The tetracoordinate 1,2-iodoxetane oxidized alcohols and a sulfide to the corresponding aldehydes and ketones, and a sulfoxide, respectively, in good to moderate yields under mild conditions. (C) 2004 Elsevier Ltd. All rights reserved.

The low sigma-donating ability of 9-phosphatriptycene 1 was revealed by cyclic voltammetry and theoretical calculations. The tungsten complex of 1 was synthesized and the IR and NMR spectroscopic data of the complex also suggested the low sigma-donating ability of 1. 1 was shown to be effective as a ligand in the palladium-catalyzed reactions, the Stille coupling and the Heck reaction.

Novel 9-phosphatriptycenes were synthesized by utilizing ortho-lithiation of a triarylphosphine oxide as a key step. The structural analysis of the 9-phosphatriptycene oxide revealed its highly distorted structure around the phosphorus atom, which is consistent with the up-field shift in the P-31 NMR spectrum. The 9-phosphatriptycene and its chalcogenides were synthesized by ordinary methods, and the spectral comparisons of these chalcogenides indicated the large s-character of the lone-pair orbital or the phosphorus-chalcogen sigma bonds of those species. The 9-phosphatriptycene oxide was reacted with lithium naphthalenide to give the ring-opened products. (C) 2004 Wiley Periodicals, Inc.

A novel synthetic route to a 9-phosphatriptycene was developed by utilizing ortho-lithiation of a triarylphosphine oxide as a key step. Systematic comparisons of the NMR spectra of 9-phosphatriptycene derivatives indicated the large s character of the lone pair orbital or the phosphorus-chalcogen bonds of the 9-phosphatriptycene derivatives.

A novel bowl-type triarylgermyl group, tris(2,2",6,6"-tetramethyl[1,1':3',l"-terphenyl-5'-yl]germyl(denoted as TRMG), was designed, and a germanol and its derivatives bearing this framework were synthesized. X-ray crystallographic analysis of TRMG-OH (5) revealed that there is no OH... O hydrogen bonding between adjacent molecules, although the possible presence of a weak intermolecular OH... pi interaction was suggested. In sharp contrast to organogermanols known so far, 5 is extremely resistant to self-condensation; no digermoxane was obtained when 5 was subjected to the conditions under which Ph3GeOH (8) affords the corresponding digermoxane. On the other hand, germanol 5 was readily converted to various derivatives. The crystal structure of TRMG-SH (12) was also determined.

An E,E-1,1,3,3-tetrafluoro-1,3-bis[2-(phenylazo)phenyl]-1,3-disiloxane (E,E-2) was synthesized by hydrolysis of E-trifluoro[2-(phenylazo)phenyl]silane (E-1). Its structure was characterized by H-1-, C-13- F-19-, and Si-29-NMR spectroscopy and X-ray crystallographic analysis showing two pentacoordinate silicon atoms with Si-N interactions. Photoirradiation of E,E-2 caused both isomerization of the azo group and formation of the corresponding Z-1 in a short time, while upon standing in the dark the E-1 was formed very slowly. (C) 2003 Elsevier B.V. All rights reserved.

Title compounds containing tetracoordinate sulfur, pentacoordinate sulfur, tetracoordinate selenium and tetracoordinate tellurium together with oxygen or nitrogen were successfully synthesized as stable compounds. Some compounds have the Martin ligand that is well-known to stabilize such high coordinate main group compounds, while others have another four-membered ring. X-ray crystallographic analyses revealed that the compounds have distorted trigonal bipyramidal (TBP) or pseudo TBP structures. In marked contrast to group 13-15 element analogues, which afford the corresponding olefins on heating, their thermolyses gave the corresponding oxiranes or an aziridine except for a few 1,2-oxachalcogenetanes, suggesting the possibility that these compounds are intermediates of the Corey-Chaykovsky reaction of chalcogen ylides with carbonyl compounds or imines. The stereochemistry (retention of configuration) of some oxirane formation reactions as well as compounds synthesized by other groups is also described. (C) 2003 Elsevier B.V. All rights reserved.

A novel heterocyclic compound, 1,3,2,5-ox-azaphosphagermolidin-2-ium-5-uide, was synthesized by sequential treatment of HMPA with t-BuLi and a hydrogermane, and its crystal structure was established by X-ray crystallographic analysis.

"Cycloaddition Reactions of an Iminophosphorane Bearing the Martin Ligand with Some Double-Bond Compounds: Syntheses, Structures and Thermolyses of a 1,3,2λ<sup>5</sup>-Oxazaphosphetidine and a 1,3,2λ<sup>5</sup>-Diazaphosphetidine-4-thione" "jointly authored"