Intramolecular cyclopropanation of an aromatic nucleus by an alkylidenecarbene: a novel access to heptafulvenes

Brückmann, Ralf; Maas, Gerhard

doi:10.1039/c39860001782

Cited by 7 publications

(1 citation statement)

References 2 publications

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“…Ϫ NMR: Bruker AMX 500 ( 1 H: 500.14 MHz; 13 C: 125.77 MHz; 31 P: 202.48 MHz); CDCl 3 was used as solvent. The following references were applied: internal TMS for the proton spectra, the solvent signal for the 13 Ϫ The following compounds were prepared by literature methods: diazo ketone 8, [17] 1,2,3-diazaphospholes 9a, [18] 9b, [19] 9c. [19] Synthesis of 5- Alkylidene-5,7a-dihydro-3H-[1,2,4]diazaphospholo-[4,3-c][1,2,3]diazaphospholes 10a؊c.…”

Section: Methodsmentioning

confidence: 99%

Polycyclic Isophosphindole Derivatives by Intramolecular Trapping of 2‐Phospha‐1,3‐diyls or Isomeric Bis(methylene)phosphoranes

Kerth

Maas

2001

European J Organic Chem

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Section: Methodsmentioning

confidence: 99%

Polycyclic Isophosphindole Derivatives by Intramolecular Trapping of 2‐Phospha‐1,3‐diyls or Isomeric Bis(methylene)phosphoranes

Kerth

Maas

2001

European J Organic Chem

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Silicon‐Substituted Carbenes

Maas

2009

Patai's Chemistry of Functional Groups

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Thermal Decomposition of α‐Diazo‐α‐(trialkylsilyl)alkanones – Intramolecular C/H Insertion of Siloxyalkylidenecarbene Intermediates

Brückmann

Maas

1987

Chem. Ber.

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a-Diazo-a-(trialkylsilyl)alkanones 6 have been prepared by silylation of primary a-diazo ketones 4 with trialkylsilyl triflates 5. Diazo compounds 6 are decomposed in boiling benzene to give l-oxa-2-sila-4-cyclopentenes 7 and 9. Evidence is presented that this transformation proceeds via alkylidenecarbenes 17 which undergo 1,5-cyelization by carbcne insertion into a Sic-H bond.The synthetic potential of a-diazocarbonyl compounds rests to a marked extent on their lability towards UV light, elevated temperature, and certain transition metals, which makes them a convenient and easily accessiblc source of carbenes or carbenoids".However, there is an obvious lack of information concerning the chemistry of a-(silyldiazomethyl)arbonyl compounds. Silylated diazo esters (la) and some r*-(silyldiazomethyl) ketones of type 1 b represent the exceptions; the prime interest in their chemistry was directed towards the eventual formation of silenes from silylated ketocarbenes derived from 1 a, b2'. As the sole "simple" silylated diazo ketone, 1 -diazo-1 -(triethylsilyl)-2-propanone has been prepared, and its thermal decomposition in the presence of copper has been studied 31. Recently, we have reported that (aroyldiazomethy1)silanes 1 c easily sulTer thermal dediazoniation with transformation into siloxyalkynes 34! Siloxyalkylidene carbenes 2 are considered the immediate precursors of the alkynes. The 1,2-aryl migration which brings about the transformation 2+3 has precedent in earlier work of Stangs', Gilbert ", and their coworkers who have shown that in alkylidenecarbenes [Ar(R)C=C:, R = alkyl, aryl] the aryl shift is usually faster than any other intra-or intermolecular trapping reaction of this carbene. On the other hand, an alkyl group is not prone to a facile 1,2-migration to the vinylidene carbon, as several successful intermolecular trapping rcactions of alkylidenecarbenes bearing Balky1 groups indicate"". We have therefore synthesized (alkanoyldiazomcthyl)silanes 6 which, by thermal decomposition, should give access to alkylidenecarbenes analogous to 2. Since B aryl groups were no longer present. the way seemed to be paved for other intra-or intermolecular reactions of these reactive intermediates. R,Si-C-CO,R Me3SiMe2C-CR III1 Synthesis of u-Diazo-a-(trialkylsilyl)alkanones 6The silylated adiazo ketones 6 are obtained under mild conditions in satisfactory to good yields by an electrophilic diazoalkane substitution at primary a-diazo ketones 4 with highly electrophilic trialkylsilyl triflates 5 as silylating reagents. This method had been used before for C-silylation of diazomethane*), ethyl diazoacetate**", (diazomethy1)phosphoryl compounds"', and diazo ketones ArCOCHN;'. Other approaches to silylated a-diazo ketones are given by acylation of lithio(pentamethyldisilanyl)diazomethane'l) and by the reaction between bis(triethylsily1)mercury and mercury-bis(diazo ketones), Hg[C(N2)COR];'; the latter reaction made diazo ketone 6aA available3'. As in the case of (aroyldiazomethy1)silanes 1 c4), the high lability of the C(N2...

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Intramolecular cyclopropanation of an aromatic nucleus by an alkylidenecarbene: a novel access to heptafulvenes

Cited by 7 publications

References 2 publications

Polycyclic Isophosphindole Derivatives by Intramolecular Trapping of 2‐Phospha‐1,3‐diyls or Isomeric Bis(methylene)phosphoranes

Polycyclic Isophosphindole Derivatives by Intramolecular Trapping of 2‐Phospha‐1,3‐diyls or Isomeric Bis(methylene)phosphoranes

Silicon‐Substituted Carbenes

Thermal Decomposition of α‐Diazo‐α‐(trialkylsilyl)alkanones – Intramolecular C/H Insertion of Siloxyalkylidenecarbene Intermediates

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