川島 隆幸

Title tandem reaction was achieved by using alpha-(trimethylsilyl)alkylphosphine chalcogenides and the lithio derivative of 2-hydroxytetrahydropyran. The Horner-Emmons reaction of the tandem products was accomplished to give the corresponding 2-(beta-styryl)tetrahydropyran derivatives by in situ generation and trapping of alpha-lithio derivatives, followed by Warren's method of olefination.

Pentacoordinate oxaphosphetanes, oxasiletanides, oxagermetanides, oxastannetanides, and tetracoordinate oxaboretanides were successfully synthesized as stable intermediates of the Wittig reaction, the Peterson reaction, Peterson-type reactions, and boron-Wittig reaction, respctively. Tetracoordi nate and pentacoordinate oxathietanes, tetracoordinate oxaselenetanes and pentacoordinate azaphosphetidines were also synthesized as their sulfur and selenium-analogs, and aza-analog of oxaphosphetanes. The X-ray crystallographic analyses of Si, Ge, P, S, and Se compounds indicated that they have a distorted trigonal bipyramidal structure with two apical oxygen atoms, but those of B, Sn, and another type of Ge compounds demonstrated that they have a very distorted tetrahedral boron, a nearly square pyramidal tin, and a tetrahedral germanium strongly interacting with an oxide anion, respectively. Expectedly, on heating all compounds containing group 13, 14, and 15 elements underwent the Wittig-type reaction to give the corresponding olefins. Although the thermolysis of oxachalcogenetanes with a tetracoordinate and pentacoordinate S and Se centers gave no olefin, it was suggested that the former compounds are intermediates of the Corey-Chaykovsky reaction of sulfur ylides.

A pentacoordinate 1,2-oxagermetanide 1, K+ 18-crown-6{[-C6H4C(CF3)(2)O-]GePh[-CH(CH(2)(t)Bu)C(CF3)(2)O-]}(-), was quantitatively synthesized as a colourless block (m.p. 217-218 degrees C (decomp.)) by deprotonation of the corresponding beta-hydroxygermane 2, [-C6H4C(CF3)(2)O-]GePhCH(CH(2)(t)Bu)C(CF3)(2)OH, which can be prepared by unique cycloelimination of benzene from o-HO(CF3)(2)CC(6)H(4)GePh(2)[CH(CH(2)(t)Bu)C(CF3)(2)OH] (3). On heating in CD3CN at 150 degrees C for 30 days, 1 equilibrates with another diastereomer 4 and then undergoes the Peterson-type reaction to give the corresponding olefin 5, (F3C)(2)C=CHCH(2)(t)Bu (13%), and its double-bond migrated isomer 6, (F3C)(2)CHCH=CH(t)Bu (33%). The yields of the olefins 5 and 6 are not very high, because their polymerization takes place under the reaction conditions. X-ray crystallographic analysis of 1 shows that it has a distorted trigonal bipyramidal structure with two oxygen atoms at apical positions.

Reaction of Se-Alkyl phosphinoselenoates with organometallics resulted in a selective attack on the selenium atom. Sequential treatment of optically active Se-benzyl t-butylphenylphosphinoselenoate with PhLi and then with electrophiles, such as alkyl halides, an alpha,beta-unsaturated ester, and chalcogen atoms, gave optically active phosphorus compounds in 5-91% yields and in high optical yields, with retention of configuration at the phosphorus atom, along with a quantitative yield of benzyl phenyl selenide.

Sterically congested thiiranes having a 2,4,6-tri-t-butylphenyl group were synthesized by the reactions of (2,4,6-tri-t-butyl)thiobenzaldehyde with sterically hindered diazo compounds. Thermal desulfurization of the most congested thiirane, 2,2-di-t-butyl-3-(2,4,6-tri-t-butylphenyl)thiirane (15c), did not proceed even upon using highly reactive reagents, such as hexamethylphosphorous triamide or organolithiums. The photoreaction of 15c did not give the corresponding styrene, but afforded several products containing 2,4,6-tri-t-butylbenzo[b]thiophene and Dewar benzenes, 2,2-di-t-butyl-3-(3,4,6-tri-t-butylbicyclo[2.2.0]hexa-2,5-dien- 2-yl)thiirane and 2-t-butyl-3,3-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-diene-2-yl)-1-butene (24), the latter of which is the first example for a vinyl-substituted Dewar benzene. Compound 24 has a unique reactivity, giving a rearrangement product, 2-t-butyl-3,3-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-diene-2-yl)-1-butene on thermolysis.