A Controlled Synthesis of 9α-Methyl- and 9α-Cyanoisocarbacyclins

Hashimoto, Shunichi; Suzuki, Atsushi; Shinoda, Tomohiro; Miyazaki, Y.; Ikegami, Shiro

doi:10.1246/cl.1992.1835

Cited by 7 publications

(1 citation statement)

References 21 publications

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“…The synthesis of hydrogenated pentalene ketone intermediates has found applications in obtaining new drugs, of which the best known are carbacyclin [ 1 ] and isocarbacyclin [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ] analogues, cioctol [ 9 ] and a few antibacterial [ 10 ] and antitumor natural products [ 11 , 12 ]. In carbacyclin synthesis, the standard key intermediate I has a symmetric ketone for linking the α-side chain by a Wittig E -olefination (at the ω-side chain) and a R group which finally is transformed into an aldehyde used to introduce the ω-side chain by a stereoselective Wardworth-Emmons E -olefination with a phosphonate ( Figure 1 ) [ 13 , 14 , 15 , 16 ].…”

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confidence: 99%

Hydroboration-Oxidation of (±)-(1α,3α,3aβ,6aβ) -1,2,3,3a,4,6a-Hexahydro-1,3-pentalenedimethanol and Its O-Protected Derivatives: Synthesis of New Compounds Useful for Obtaining (iso)Carbacyclin Analogues and X-ray Analysis of the Products

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Cãproiu³

et al. 2017

Molecules

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Hydroboration-oxidation of 2α,4α-dimethanol-1β,5β-bicyclo[3.3.0]oct-6-en dibenzoate (1) gave alcohols 2 (symmetric) and 3 (unsymmetric) in ~60% yield, together with the monobenzoate diol 4a (37%), resulting from the reduction of the closer benzoate by the intermediate alkylborane. The corresponding alkene and dialdehyde gave only the triols 8 and 9 in ~1:1 ratio. By increasing the reaction time and the temperature, the isomerization of alkylboranes favours the un-symmetrical triol 9. The PDC oxidation of the alcohols gave cleanly the corresponding ketones 5 and 6 and the deprotection of the benzoate groups gave the symmetrical ketone 14, and the cyclic hemiketal 15, all in high yields. The ethylene ketals of the symmetrical ketones 11 and 13 were also obtained. The compounds 5, 6, 11, 13, 14 could be used for synthesis of new (iso)carbacyclin analogues. The structure of the compounds was established by NMR spectroscopy and confirmed by X-ray crystallography.

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Section: Introductionmentioning

confidence: 99%

Hydroboration-Oxidation of (±)-(1α,3α,3aβ,6aβ) -1,2,3,3a,4,6a-Hexahydro-1,3-pentalenedimethanol and Its O-Protected Derivatives: Synthesis of New Compounds Useful for Obtaining (iso)Carbacyclin Analogues and X-ray Analysis of the Products

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Cãproiu³

et al. 2017

Molecules

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TheStille Reaction

1997

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Examples of the palladium‐catalyzed coupling of organotin compounds with carbon electrophiles were first reported in 1977 by Kosugi, Shimizu, and Migita. The first study by Stille appeared in 1978. The early work of Beletskaya, using “ligandless” catalysts in cross‐coupling reactions, also often employed organostannanes. In recognition of Stille's comprehensive synthetic and mechanistic studies, this coupling is now referred to as the Stille reaction. R 1 is typically an unsaturated moiety (e.g., vinyl, aryl, heteroaryl, alkynyl, allyl) or less often an alkyl group, and R 2 , the nontransferable ligand, is almost always butyl or methyl. Electrophiles participating in the coupling include halides (almost always bromides or iodides) and sulfonates (most often used are the triflates). Other leaving groups have been used in special cases. The Stille reaction belongs to the larger family of palladium‐ and nickel‐catalyzed cross‐coupling reactions which features, e.g., organomagnesium, organozinc, organoboron, and organosilicon reagents. Organotin reagents are air‐ and moisture‐stable organometallics, and can be conveniently purified and stored. Since they do not react with most common functional groups, the use of protecting groups is almost always unnecessary in conjunction with the Stille reaction. This is a very unusual and attractive feature for an organometallic process. Also, the reaction is often neither air nor moisture sensitive. In some cases, water and oxygen have actually been shown to promote the coupling. Although the reaction as initially described by Stille is often carried out under rather drastic conditions (temperatures of ≥100° are not uncommon), newly developed ligand 11 and the addition of copper(I) salts have solved some of the problems associated with low reactivity. The utility and mildness of the Stille reaction are demonstrated by its frequent use in the final stages of complex natural product syntheses. This chapter attempts a critical and comprehensive coverage of the reaction scope. Mechanistic description of the reaction is rather brief, and the reader is referred to the pertinent literature for a more detailed analysis. All of the relevant literature is covered up to the end of 1994. The reaction was reviewed by Stille in 1986, and by Mitchell in 1992; a rather comprehensive account by Farina and Roth has appeared more recently. Developments that occurred in 1995, as this work was in progress, and that were deemed important were incorporated as much as possible in this review.

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Organotin Reagents in Cross‐Coupling

Mitchell¹

1998

Metal‐Catalyzed Cross‐Coupling Reactions

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Organotin compounds offer many advantages for cross-coupling reaction, and it is thus not surprising that the palladium-catalyzed procedure introduced and developed by the late John Stille was seized upon by preparative organic chemists and used to great advantage for synthetic elaborations. Stille himself reviewed the area in 1986 [ 111, but his untimely death in July 1989 cut short his own work on the reaction which now bears his name. The present author attempted to cover the progress of the "Stille reaction" over the period 1986-mid-1991 in a review published in 1992 [2], and the publication of this monograph provides an opportunity to take another critical look at the applications of the procedure.In the early days various palladium catalyts were used, Pd(PPh,), and PhCH,PdCI(PPh,), being the two which were most frequently applied. A considerable amount of work has since gone into catalyst refinement, and here the name of V. Farina must be mentioned; he has published a number of important papers, and also reviewed his work and that of others [3]. Readers who wish to keep themselves up to date in this area in the future must hope that L. S. Hegedus will "keep up the good work' and continue to publish his invaluable annual surveys on the use of transition metals in organic synthesis [4] which always contain a section on tin compounds.Though strictly speaking outside the scope of this chapter, some brief details of other palladium-catalyzed reactions of organotin compounds (ditins and tin hydrides) will be given, as these can provide potentially useful reagents for Stille reactions. Many transition metals have found their niche in organic synthesis, but as far as reactions of organotins are concerned only palladium has been used to a large extent. However, relevant reactions of two other transition metals, copper and nickel, will be referred to at the end of this survey.One of the beauties of the Stille procedure is that various organic residues (alkyl, aryl, vinyl, alkynyl, etc.) can be transferred from tin to carbon in cross-couplings; although papers still continue to appear which deal with the transfer of more than one type of residue, "dedicated" papers whose goal is a particular type of elaboration are more common, and indeed there is a type of "hit list" reflecting the popularity of certain groups. Alkenyltins are by far the most important on this list, and we shall start by discussing their use; subsequent sections will mirror the range of application of other types of organotin. Stille Coupling of AlkenyltinsAlkenyltins can undergo coupling with a wide variety of organic halides and triflates and with acid chlorides. Although most of the examples reported deal with intermolecular coupling, intramolecular coupling is finding increasing favor, particularly as a step in 167 Metal-catalyzed Cross-coupling Reactions Edited by François Diederich, Peter J. Stang 4 Orgunotin Reqents in Cross-couplingnatural-product synthesis. The presence of two stannyl groups on the ethene unit offers synthetic advantages...

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A Controlled Synthesis of 9α-Methyl- and 9α-Cyanoisocarbacyclins

Cited by 7 publications

References 21 publications

Hydroboration-Oxidation of (±)-(1α,3α,3aβ,6aβ) -1,2,3,3a,4,6a-Hexahydro-1,3-pentalenedimethanol and Its O-Protected Derivatives: Synthesis of New Compounds Useful for Obtaining (iso)Carbacyclin Analogues and X-ray Analysis of the Products

Hydroboration-Oxidation of (±)-(1α,3α,3aβ,6aβ) -1,2,3,3a,4,6a-Hexahydro-1,3-pentalenedimethanol and Its O-Protected Derivatives: Synthesis of New Compounds Useful for Obtaining (iso)Carbacyclin Analogues and X-ray Analysis of the Products

TheStille Reaction

Organotin Reagents in Cross‐Coupling

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