Transition-metal-catalyzed decomposition of silylated diazoacetic esters: influence of silicon substituents, catalyst, and solvent on product formation

Maas, Gerhard; Gimmy, M.; Alt, Mechthild

doi:10.1021/om00059a052

Cited by 31 publications

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“…Surprisingly, although the alkynyl group is described in reviews to behave as a donor substituent for carbenoid intermediates, the use of alkynyldiazo compounds in Rh(II) catalyzed insertion reactions has never been described and only a single example of cyclopropanation based on such a reagent has been reported . Similarly, despite the stability provided to diazocompounds by a trimethylsilyl group, the reactivity studies of Rh(II) α-silylated carbenoids generated from this class of reagents are rare . We recently described a general access to α-silylated alkynylhydrazones from mixed dimethylalkynylaluminum reagents and trimethylsilyl (TMS) diazomethane (Scheme ).…”

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Rhodium(II)-Alkynyl Carbenoids Insertion into Si–H bonds: An Entry to Propargylic Geminal Bis(silanes)

et al. 2016

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Rhodium(II)-Alkynyl Carbenoids Insertion into Si–H bonds: An Entry to Propargylic Geminal Bis(silanes)

et al. 2016

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“…For example, UV irradiation of the SiEt 3 and SiPr i 3 substituted diazoacetates in benzene was unspecific while their copper-or rhodiumcatalysed decomposition gave products derived from other carbene-type reactions. 20 a-Alkoxy(diisopropyl)silyl-a-diazoacetates, on the other hand, underwent a photochemical 1,5-C-H insertion of the carbene at the alkoxy chain but no 1,4-C,H insertion at the isopropyl substituents. 13 In spite of these apparent structural limitations, it is obvious that the transformation 1 ?…”

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Synthesis and ring enlargement of 2-ethoxycarbonyl-1-silacyclobutanes

Maas

Bender

2000

Chem. Commun.

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“…1,2(C→C) migration of an alkoxy group] can often be suppressed by a suitable choice of substituents and reaction conditions in favor of carbene or carbenoid reactions involving the silyl group. The range of possibilities 1,4 comprises the carbene-to-silene rearrangement 3,5,6 [i.e. 1,2(Si→C) substituent migration], and the formation of silaheterocycles by intramolecular reactions such as C,H insertion, 7,8 cyclopropanation, 7 and attack at C,C triple bonds.…”

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Novel α-Silyl-α-diazoacetates Containing a Silicon-Heteroatom Bond

Maas¹

1999

Synthesis

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Silylation of diazoacetic esters with (t-Bu) 2 Si(Cl)OTf or Ph(t-Bu)Si(Cl)OTf (Tf = SO 2 CF 3 ) yields a-(chlorosilyl)-a-diazoacetates 3a-d, which can be converted into azidosilyl-(7), isocyanatosilyl-(8), and isothiocyanatosilyl-(9) substituted diazoacetates. Acid-catalyzed hydrolysis of 8a or 9a generates (hydroxysilyl)diazoacetate 10. (Allylaminosilyl)diazoacetates 12a,b can be prepared from diisopropylsilyl bis(triflate) by successive treatment with diazoacetic esters and allylamine.Silyl-substituted diazoalkanes and diazocarbonyl compounds are the precursors of choice for the photochemical, thermal, or transition metal-catalyzed generation of silyl carbenes or carbenoids. 1,2 The substituents attached to silicon can become actively involved in subsequent intramolecular reactions of these short-lived intermediates. Especially useful in this respect are a-silyl-a-diazoacetates, for which the traditional Wolff rearrangement 3 [i.e. 1,2(C→C) migration of an alkoxy group] can often be suppressed by a suitable choice of substituents and reaction conditions in favor of carbene or carbenoid reactions involving the silyl group. The range of possibilities 1,4 comprises the carbene-to-silene rearrangement 3,5,6 [i.e. 1,2(Si→C) substituent migration], and the formation of silaheterocycles by intramolecular reactions such as C,H insertion, 7,8 cyclopropanation, 7 and attack at C,C triple bonds. 9 So far, only silyl diazoacetates with alkyl, aryl, trimethylsilyl, and RO substituents attached to silicon have been studied. Other hetero substituents at silicon might generate carbene-derived organosilicon compounds with additional functionality at silicon or even give rise to new reactivity patterns. Under these aspects, we decided to synthesize azidosilyl-, isocyanatosilyl-, isothiocyanatosilyl-and aminosilyl-substituted diazoacetates, all of which have a silicon-nitrogen bond in common.Silicon-functionalized a-silyl-a-diazoacetates are prepared conveniently from silyl-bis(triflates) by successive treatment with a diazoacetic ester and a (hetero)nucleophile in the presence of a tertiary amine. 10 It was reported recently that under appropriate conditions, the twofold nucleophilic substitution of dichlorosilanes can be achieved as well. 8 Preliminary experiments, in which a (trifloxysilyl)diazoacetate was treated with sodium azide, surprisingly did not lead to a clean product. Therefore, we turned our attention to chlorosilyl triflates 1 11 and 2. 12 Since the triflate anion is a much better leaving group than chloride, selective introduction of one nucleophile or stepwise introduction of two different nucleophiles is possible, as has been demonstrated for the successive reaction of 1 with an allylic alcohol and an enolate. 11Reaction of 1 with ethyl or methyl diazoacetate in the presence of ethyldiisopropylamine provided (chlorosilyl)diazoacetates 3a,b in good yields (Scheme 1). Chlorosilyl triflate 2 was transformed into 3c,d analogously. As expected, this electrophilic diazoalkane substitution process 13 occurred exclusive...

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Transition-metal-catalyzed decomposition of silylated diazoacetic esters: influence of silicon substituents, catalyst, and solvent on product formation

Cited by 31 publications

References 0 publications

Rhodium(II)-Alkynyl Carbenoids Insertion into Si–H bonds: An Entry to Propargylic Geminal Bis(silanes)

Rhodium(II)-Alkynyl Carbenoids Insertion into Si–H bonds: An Entry to Propargylic Geminal Bis(silanes)

Synthesis and ring enlargement of 2-ethoxycarbonyl-1-silacyclobutanes

Novel α-Silyl-α-diazoacetates Containing a Silicon-Heteroatom Bond

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