Some reactions of 3-ethoxy-1,2,3-triphenylcyclopropene

Monahan, Audrey S.; FREILICH, J. D.; Fong, J

doi:10.1016/s0040-4039(01)98103-1

Cited by 10 publications

(9 citation statements)

References 4 publications

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“…Similarly, heating a sample of compound (10) afforded a mixture of (1 1) and ( 13). One additional point worth noting is that thiophens (9) and (12) [as well as (1 1) and ( 13)] are readily interconverted under the reaction conditions employed.…”

Section: Resultsmentioning

confidence: 99%

Photochemistry of cyclopropene derivatives. Ring-opening reaction of 3-heteroaryl substituted cyclopropenes

Chiacchio¹,

Compagnini²,

Grimaldi³

et al. 1983

J. Chem. Soc., Perkin Trans. 1

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The photochemical rearrangement of several 3heteroaryl substituted cyclopropenes has been studied. The rearrangements are derived from the '~t--'lt* singlet state of the cyclopropene. Ring opening occurs to give a vinylcarbene intermediate which undergoes a subsequent electrocycliration. The transient intermediate so produced can undergo either a 1,3-or a 1,5-sigmatropic hydrogen shift to give the observed products. One strong piece of evidence for carbene intervention is the observation of a 1,3-butadiene derivative as one of the photoproducts obtained from the photolysis of a 3-pyrrolyl substituted cyclopropene. The 1,3-diene is thought to be derived by insertion of the vinylcarbene into the neighbouring methyl group. The regioselectivity of the rearrangement can be accounted for in terms of competitive 1,3and 1,5-sigrnatropic hydrogen migrations.

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Section: Resultsmentioning

confidence: 99%

Photochemistry of cyclopropene derivatives. Ring-opening reaction of 3-heteroaryl substituted cyclopropenes

Chiacchio¹,

Compagnini²,

Grimaldi³

et al. 1983

J. Chem. Soc., Perkin Trans. 1

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“…This latter product is also formed upon reaction of l a with [(C,H,)PtCl,], [l 11 or with an acid catalyst [12]. 3-Alkoxy-substituted triphenylcyclopropenes l b [13] and l c undergo the same transformation and afford the substituted indenes 5b and 5c, but in this case only the Cu(1) catalysts are effective. With lb, Rh,(PFB), produced only the unsaturated ketone 6, which originates from ring opening [16] in essentially quantitative yield, took place.…”

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confidence: 99%

Rh(II)‐Catalyzed Isomerizations of Cyclopropenes Evidence for Rh(II)‐Complexed Vinylcarbene Intermediates

Müller

Pautex

Doyle

et al. 1990

Helvetica Chimica Acta

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The thermocatalytic rearrangements of cyclopropenes 1 4 have been investigated in the presence of Rh(I1) perfluorobutyrate. 1,2,3-Triphenylcyclopropene (la) undergoes rearrangement to diphenylindene 5a or, with alkoxycyclopropene derivatives, to ccJ-unsaturated ketone 6. Furan formation occurs with 2,3-diphenylcyclopropenecarboxylate 2, but the diethyl counterpart 3 rearranges to dienoate 8.2-Alkylcyclopropenecarboxylates 4 afforded (E)-methylidenecyclopentane derivatives9 as the only isolable product in yields of ca. 35 %. A mechanism involving regio-and stereospecific cyclopropene ring opening to a Rh-complexed vinylcarbene and insertion of the latter into the C-H bond to give 9 is proposed. An analogous mechanism should account for the rearrangement products of 1 to 3.

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“…It is well known that suitably substituted cyclopropenes undergo both cycloaddition and complexation with transition metal complexes as a mean of releasing strain. [26][27][28] This intermediate could undergo a reversible electrocyclic [ p 2 s + s 2 s ] ring opening 29 to give the corresponding Rh-coordinated vinylcarbene 10 which can exist as an E/Z set of diastereomers. More than likely, the formation of 3/4 proceeds by equilibration of the (E)-and (Z)-vinylcarbenoids in analogy with the isomerisation observed in related thermal and photochemical cyclopropene-vinylcarbene rearrangements.…”

Section: Equationmentioning

confidence: 99%

Synthesis of Furocoumarins via Rhodium(II)-Catalysed Heterocyclisation of 3-Diazobenzopyran-2,4-(3H)-dione with Terminal Alkynes

Tollari¹,

Palmisano²,

Cenini³

et al. 2001

Synthesis

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The rhodium (II) acetate-catalysed decomposition of 3-diazobenzopyran-2,4(3H)-dione in the presence of a terminal alkyne gave rise to a mixture of isomeric 2-substituted furo [3,2-c]coumarin and furo [2,3-b]coumarin, resulting from a formal [3+2] cycloaddition.It is about 100 years since Silberad and Roy 1 first recognised a-diazocarbonyl compounds as precursors of carbenoid specie(s) when exposed to metal salts or complexes. These elusive intermediates have been continuously exploited by virtue of their manifold reactivity, mainly addition to multiple bonds in both inter-and intramolecular contexts and insertion to X-H bonds. [2][3][4] Since their discovery, several modifications for the metalinduced decomposition process emerged and a variety of transition metal-complexes have proven to be an invaluable tool in aiding this goal. Among them, Rh(II) dicarboxylates Rh 2 (m-O 2 CR) 4 , dinuclear molecules of D 4 symmetry and vacant coordination site at each metal atom, deserve mention. In particular, dirhodium(II) tetrakis(acetate) [Rh 2 (OAc) 4 ], pioneered by Paulissen et al. 5 to generate carbenoid species, represents the most popular and most frequently used catalyst, thus significantly expanding the domain of carbene chemistry. [6][7][8][9][10][11][12][13] As a part of our studies in this area, 14,15 we investigated the fate of the transient electrophilic Rh-carbenoid generated from 3-diazobenzopyran-2,4(3H)-dione (1) 16 (hereafter called diazocoumarin) in the presence of several differently substituted alkynes 2a-f (Eq.1).Recent studies concerning the Rh(II)-catalysed reaction of 1 by Lee and co-workers 17 prompt us to communicate our results in the related studies. Herein, we report that such process provides a straightforward entry to natural and unnatural members of furocoumarins, a class of compounds that are endowed with a vast range of biological activities. [18][19][20][21][22][23] Our preliminary studies were carried out with phenylacetylene (2a) as a model alkyne and a number of variations in nature of catalyst [e.g., Rh(PPh 3 ) 3 Cl, Rh 2 (OAc) 4 , CuOTf, Cu(acac) 2 , Ru(PPh 3 ) 3 Cl 2 ], solvent (e.g., fluorobenzene, CH 2 Cl 2 , CCl 4 , p-xylene, 1,3-dichlorobenzene) and reaction conditions were also explored. The best compromise between selectivity and conversion of 2a (2 equiv) was displayed by Rh 2 (OAc) 4 (2 mol%) which, in fluorobenzene at 90°C in a screw-capped vial, effected a 100% conversion of 1 after 2 hours, producing a 76% of a mixture of 3a and 4a in a 1:1.2 ratio. Accordingly, the rate of formation and the yields of 3a/4a increased when the catalyst loading was increased from 1 mol% to 2 mol%, while further increase in the amount of catalyst was not effective giving comparable yields. Although the Rh-carbenoid system from 1 reacted slowly with fluorobenzene giving mainly 3-(4-fluorophenyl)-4-hydroxycoumarin (5) (Figure 1), the formal cycloaddition with alkynes was generally faster, with the exception of 2e (vide infra). 24,25

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Some reactions of 3-ethoxy-1,2,3-triphenylcyclopropene

Cited by 10 publications

References 4 publications

Photochemistry of cyclopropene derivatives. Ring-opening reaction of 3-heteroaryl substituted cyclopropenes

Photochemistry of cyclopropene derivatives. Ring-opening reaction of 3-heteroaryl substituted cyclopropenes

Rh(II)‐Catalyzed Isomerizations of Cyclopropenes Evidence for Rh(II)‐Complexed Vinylcarbene Intermediates

Synthesis of Furocoumarins via Rhodium(II)-Catalysed Heterocyclisation of 3-Diazobenzopyran-2,4-(3H)-dione with Terminal Alkynes

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