Generation and Decomposition of a Pentacoordinate Spirobis[1,2-oxasiletanide]

Kawashima, Takayuki; Naganuma, Kenji; Okazaki, Renji

doi:10.1021/om970459a

Cited by 35 publications

(7 citation statements)

References 18 publications

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“…Then, a [2+2] retro-cycloaddition, probably induced by a release of ring strain in the pentacoordinate intermediate 5, similarly to the Perterson olefination reaction, affords 4. [20,21] The efficient stabilization of silanoic acid 6 by coordination of the donor/acceptor iminophosphorane ligand 7 on the silanone function was supported by DFT calculations revealing the strong exergonic nature of the reaction (DG = À44.2 kcal mol À1 , Scheme 5). Interestingly, in spite of this stabilization, the coordination of ligand 7 does not affect the acidity in the gas phase.…”

Section: Methodsmentioning

confidence: 88%

A Base‐Stabilized Sila‐β‐Lactone and a Donor/Acceptor‐Stabilized Silanoic Acid

et al. 2013

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The carbonyl group I is ubiquitous and without doubt one of the most important functional groups in organic chemistry; it characterizes many compounds such as ketones, aldehydes, carboxylic acids, and many other related compounds. In marked contrast, the synthesis of the heavier silicon analogue II is still elusive owing to the weak and strongly polarized Si-O p bond, which accounts for a very strong tendency to give thermodynamically stable polysiloxanes.[1]M. Driess and co-workers reported that the silanone function can be efficiently stabilized using a donor/acceptor system III.[2-3] A base-stabilized silanon complex with a transition metal (type III) has also recently been reported.[4] M. Driess and co-workers also demonstrated that the stabilization of such species can be achieved by coordination of electron-donating ligands on the silicon center (type IV), which allowed the isolation of the first examples of a basesupported silaurea [5] and a silanoic silyl ester V.[6] We have also recently reported the synthesis of the first donorstabilized silacyclopropan-1-one of type IV.[7] Although these techniques allowed the synthesis of other silacarbonyl derivatives, such as silanoic acid anhydride VI [8] and pyridinium salts of silanoic acid VII, [9] only a few types of silacarbonyl compounds are available to date.[10] Here we present the synthesis of the first base-stabilized sila-b-lactone VIII and its unique reactivity with alcohols leading to the formation of a silanoic acid IX, more precisely, silicic acid monoethyl ester, which is a silicon analogue of monoethyl carbonate.It was known that silylenes react with dioxygen (O 2 ) to generate the corresponding transient silaester.[11] Similarly, the base-stabilized silacycloprop-1-ylidene 1 [12] readily reacts with one equivalent of dioxygen at 5 8C to give selectively the corresponding base-supported sila-b-lactone 2 (Scheme 1).The reaction proceeds regio-and diastereoselectively, which was indicated by the 31 P NMR spectrum showing only two signals for the b-lactone 2 in the same proportions as those for 1 (51.3 and 47.7 ppm; diastereomer ratio: 92:8). Derivative 2 is stable under inert conditions and was isolated as colorless crystals in 51 % yield. In the 29 Si NMR spectrum the signal corresponding to the silanone function appears as a doublet (d = À52.7 ppm, 2 J PSi = 11.2 Hz) at slightly lower field compared to 1 (d = À87.5 ppm), but in the range of base-stabilized silanones. [5,7] The two carbon atoms of the lactone ring were observed as two doublets at relatively low field (d = 80.1 ppm, 1 J CP = 85.8 Hz and d = 47.4 ppm, 2 J CP = 13.6 Hz). The 1 H NMR spectrum shows a doublet for the proton of the lactone ring with a large coupling constant (d = 4.51 ppm, 3 J PH = 20.4 Hz).The structure of 2 was unambiguously confirmed by X-ray diffraction analysis (Figure 1).[13] The structure reveals an essentially planar b-lactone four-membered ring (AE8 = 359.88) with an oxygen atom (O2) inserted between the silicon (Si1) and carbon (C1) atoms attached to the phospho...

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Section: Methodsmentioning

confidence: 88%

A Base‐Stabilized Sila‐β‐Lactone and a Donor/Acceptor‐Stabilized Silanoic Acid

et al. 2013

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“…4 Most of them were isolated as stable compounds by introduction of the Martin ligand. 5 Furthermore, we have also synthesized spiro compounds bearing two oxetane rings, namely, spirobi[1,2-oxaphosphetane], 6 , spirobi[1,2-oxasiletanide], 7 and spirobi[1,2-oxaselenetane]. 8 In the last account, 9 we reported four-membered heterocycles containing highly coordinated group 16 elements.…”

Section: Introductionmentioning

confidence: 99%

Chemistry of Four-Membered Ring Compounds Containing a Hypervalent Sulfur Atom and a Heteroatom at the Neighbor Positions

Kawashima

2011

Phosphorus, Sulfur, and Silicon and the Related Elements

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Title compounds containing tetracoordinated and pentacoordinated sulfur together with oxygen, nitrogen, or sulfur were successfully synthesized as stable compounds. They contain the Martin ligand, which is well known to be able to stabilize such highly coordinated main group compounds. X-ray crystallographic analyses revealed that they have distorted trigonal bipyramidal (TBP) or pseudo-TBP structures. In marked contrast to group 13-15 element analogues, which afford the corresponding alkenes upon heating, thermolyses of compounds bearing an oxygen or nitrogen atom gave the corresponding oxiranes or aziridine, suggesting the possibility that these compounds are intermediates of the Corey-Chaykovsky reaction of sulfur ylides with carbonyl compounds or imines. Thermolysis of 1λ 4 ,2-dithietanes also gave the corresponding thiiranes. The stereochemistry (retention of configuration) of formation of these three-membered ring compounds is also described.

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“…2,3 For the purpose of elucidating the influence of ring size of the spiro-ring system on the reactivity of the heteracyclobutanes, we have investigated the synthesis and reactivity of compounds 1 and 2, which have two oxaphosphetane and oxasiletane rings, respectively, and found that 1 undergoes double olefin extrusion, 4 while 2 undergoes homo-Brook rearrangement to give the corresponding alcohol. 5 On the other hand, we have recently found that the oxirane formation reactions from pentacoordinate 1,2l 6 -oxathietanes 3a,b or tetracoordinate 1,2l 4 -oxaselenetanes 4a,b proceed with retention of configuration, 6 which is the first example for the oxirane formation without backside attack of oxide anion on the carbon attached to the chalcogen atom, in sharp contrast to the Corey-Chaykovsky reaction. 7 These results prompted us to study tetracoordinate 1,5-dioxa-4l 4 -selenaspiro [3.3]heptanes, a novel type of a spiroselenurane bearing two oxaselenetane rings.…”

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confidence: 97%

“…Fig.1ORTEP drawing of trans-trans-9 with thermal ellipsoid plot (30% probability for all non-hydrogen atoms). Selected bond lengths (Å), bond angles (°) and torsion angles (°): Se1-O1 1.971(4), Se1-O2 1.955(4), Se1-C1 1.979(6), Se1-C3 1.978(6), C1-C2 1.532(8), C2-O1 1.388(6), C3-C4 1.531(8), O2-C4 1.392(7); O1-Se1-O2 155.26(18), C1-Se1-O1 71.1(2), Se1-C1-C2 90.0(4), C1-C2-O1 103.7(5), Se1-O1-C2 94.7(3), C1-Se1-C3 109.2(3), O2-Se1-C3 71.9(2), O2-C4-C3 104.3(5), Se1-C3-C4 89.1(4); Se1-C1-C2-O1 25.9(5), Se1-C3-C4-O2 26.1(5).…”

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confidence: 99%