1,4‐Di‐tert‐butylsilabenzene: Generation and Trapping Reactions

Abstract

served for the u-peroxylactones (2) and that the electron exchange mechanism does not operate [2].On the basis of our preliminary results, we conclude that the 3-imino-I ,2-dioxetanes (3) are thermally much less stable than the u-peroxylactones and are inefficient sources for chemi-energizing electronically excited products. In this context, it is of interest that the 3-imino-1,2-dioxetanes (3) derived from N-phenyl-and N-p-tolyl-diphenylketenimines and N-p-tolyl-tert-butylketenimine via singlet oxygenation were too unstable for 'H-NMR observation even at -60 "C; only the carbonyl compound and isocyanate produced by fragmentation could be detected.

Synthesis of Stable 2-Silanaphthalenes and Their Aromaticity

“…The high stability of 1a demonstrates the excellent steric protection afforded by the Tbt group. In contrast, the tert -butyl group in 1,4-di- tert -butyl-1-silabenzene, which reportedly undergoes facile dimerization even at 0 °C, is ineffective …”

A Stable Neutral Silaaromatic Compound, 2-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}- 2-silanaphthalene

“…No dimerization product was detected, although 1 is air- and moisture-sensitive due to its SiC moiety. Its thermal stability, obviously due to the steric protecting ability of the Tbt group, is in sharp contrast to that of 1,4-di- tert- butylsilabenzene, which cannot be isolated as a monomer and undergoes facile dimerization even at 0 °C . Interestingly, 1 retains its high reactivity in spite of the thermal stability.…”

Heavy Analogs of Aromatic Compounds

“…9b Particular attention has been paid to the most fundamental prototypical silabenzene, the Me-derivative of which, 1b, (Scheme 6.1) was generated for the first time by Barton et al and whose intermediate formation was convincingly proved by its dimerization product or trapping reactions with MeOH and alkynes (HC≡CH, CF 3 C≡CCF 3 ). 16 Some other interesting examples of transient substituted silabenzenes, whose intermediacy was proved by either trapping reactions or direct spectroscopic observation in a low-temperature matrix, were reported in due course (Scheme 6.1): 1,4-di-tert-butyl-1-silabenzene 2 (formation of a [2 + 2] head-to-tail dimer, [4 + 2] cycloaddition with 1,3-dienes), 17 1-methyl-2,3,4,5-tetraphenyl-1silabenzene 3 (1,2-and 1,4-addition of MeOH and [4 + 2] cycloaddition with 2,3dimethyl-1,3-butadiene), 18 4-tert-butyl-1-methoxy-2,6-bis(trimethylsilyl)-1-silabenzene 4c (1,2-addition of MeOH), 19 1-tert-butyl-2,4,6-tris(trimethylsilyl)-1-silabenzene 4a and 1-tert-butyl-2,6-bis(isopropyldimethylsilyl)-4-trimethylsilyl-1-silabenzene 4b (matrix IR and UV spectroscopy, stable up to 90 K even without an Ar matrix). 16 Some other interesting examples of transient substituted silabenzenes, whose intermediacy was proved by either trapping reactions or direct spectroscopic observation in a low-temperature matrix, were reported in due course (Scheme 6.1): 1,4-di-tert-butyl-1-silabenzene 2 (formation of a [2 + 2] head-to-tail dimer, [4 + 2] cycloaddition with 1,3-dienes), 17 1-methyl-2,3,4,5-tetraphenyl-1silabenzene 3 (1,2-and 1,4-addition of MeOH and [4 + 2] cycloaddition with 2,3dimethyl-1,3-butadiene), 18 4-tert-butyl-1-methoxy-2,6-bis(trimethylsilyl)-1-silabenzene 4c (1,2-addition of MeOH), 19 1-tert-butyl-2,4,6-tris(trimethylsilyl)-1-silabenzene 4a and 1-tert-butyl-2,6-bis(isopropyldimethylsilyl)-4-trimethylsilyl-1-silabenzene 4b (matrix IR and UV spectroscopy, stable up to 90 K even without an Ar matrix).…”