- A novel synthesis of γ,δ-unsaturated aldehydes from α-formyl-γ-lactones
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A preparatively useful one-step transformation of γ,γ- disubstituted α-formyl-γ-lactones into trisubstituted γ,δ-unsaturated aldehydes is described, by means of catalytic amounts of either AcOH or AcOEt in the vapor phase over a glass support. A mechanistic rationale is proposed. Copyright
- Snowden, Roger L.,Brauchli, Robert,Linder, Simon
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experimental part
p. 1216 - 1225
(2011/09/16)
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- Studies on the mechanism, selectivity, and synthetic utility of lactone reduction using SmI2 and H2O
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Although simple aliphatic esters and lactones have long been thought to lie outside the reducing range of SmI2, activation of the lanthanide reagent by H2O allows some of these substrates to be manipulated in an unprecedented fashion. For example, the SmI2-H2O reducing system shows complete selectivity for the reduction of 6-membered lactones over other classes of lactones and esters. The kinetics of reduction has been studied using stopped-flow spectrophotometry. Experimental and computational studies suggest that the origin of the selectivity lies in the initial electron-transfer to the lactone carbonyl. The radical intermediates formed during lactone reduction with SmI2-H2O can be exploited in cyclizations to give cyclic ketone (or ketal) products with high diastereoselectivity. The cyclizations constitute the first examples of ester-alkene radical cyclizations in which the ester carbonyl acts as an acyl radical equivalent.
- Parmar, Dixit,Duffy, Lorna A.,Sadasivam, Dhandapani V.,Matsubara, Hiroshi,Bradley, Paul A.,Flowers II, Robert A.,Procter, David J.
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supporting information; experimental part
p. 15467 - 15473
(2010/02/16)
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- Masked ω-lithio ester enolates: Synthetic applications
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The protocol of lithiation by means of lithium and a catalytic (5% molar) amount of DTBB (4,4'-di-tert-butylbiphenyl), applied to ω-chloro ortho ester 6 under Barbier-type conditions gives, after final acid-catalyzed methanolysis, the corresponding functionalized esters 8 or 9 (for chlorotrimethylsilane as electrophile) or, after ortho ester deprotection and acid catalyzed treatment, the δ-lactones 11. The procedure is also practical for bicyclic ortho esters 14: the β-chloro OBO ester derivate generates the γ-lactones 15 and the γ-chloro OBO ester gives corresponding esters 8.
- Yus, Miguel,Torregrosa, Rosario,Pastor, Isidro M.
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p. 330 - 348
(2007/10/03)
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- Tandem cross-metathesis/hydrogenation/cyclization reactions by using compatible catalysts
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(Matrix presented) A one-pot tandem cross-metathesis/hydrogenation/cyclization procedure was achieved at room temperature, under 1 atm of hydrogen, in the presence of a ruthenium catalyst and PtO2 showing the compatibility of the two catalysts. This tandem reaction allows the synthesis of substituted lactones and lactols from acrylic acid and acrolein, respectively, in the presence of unsaturated alcohols.
- Cossy, Janine,Bargiggia, Frederic,BouzBouz, Samir
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p. 459 - 462
(2007/10/03)
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- Rhodium catalysed carbonylation of homoallylic alcohols to spiropyrans bearing quaternary centres
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A convenient preparation of substituted-spiropyrans via rhodium catalysed hydroformylation of homoallylic alcohols, followed by a condensation sequence to form hemiacetals and 2,2,3,3-tetraalkyl-4[H]- pyrans, is described.
- Kitsos-Rzychon, Beate,Eilbracht, Peter
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p. 10721 - 10732
(2007/10/03)
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- Synthesis and Applications of Tetrahydrofuran-Stable Substituted (3-Lithioxyalkyl)- and (4-Lithioxyalkyl)lithiums, Modified with Magnesium 2-Ethoxyethoxide
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Substituted hydroxyalkyl phenyl sulfides 3 have been synthesized from the corresponding allylic or homoallylic alcohols 2. Regiospecific cleavage of the C - SPh bond of the sulfides 3 by lithium dispersion in tetrahydrofuran (THF) led to the synthesis of substituted (3-lithioxyalkyl)- and (4-lithioxyalkyl)lithiums 4, most of which share the ω carbon with a carbocyclic ring. The organolithiums were modified with magnesium 2-ethoxyethoxide in order to suppress their reactivity toward THF cleavage, thus offering the advantage of preparing storable ethereal solutions of certain types of (lithioxyalkyl)lithiums. This strategy appears to be of rather broad scope. The functionalized organolithiums prepared in this way react normally with electrophilic reagents with yields in the range 35-55%. Thus, carboxylations of 4 yielded lactones 5, some of which are natural products, while reactions of 4 with benzophenone and cyclic ketones yielded 1,4- and 1,5-diols 6 and 7, respectively.
- Kostas, Ioannis D.,Screttas, Constantinos G.
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p. 5575 - 5577
(2007/10/03)
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- A new synthesis of lactones from tertiary alkenylcarbinols by cobalt-catalyzed photocarbonylation under ambient conditions
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In the presence of a Co catalyst, tertiary vinyl-, propenyl-, and allylcarbinols were chelatively cycloadded to carbon monoxide to produce lactones by xanthone-sensitized photoreaction in tetrahydrofuran, under CO at 1 atmosphere and at room temperature.At lower temperatures the isomerization of alkenyl-carbinols was suppressed and lactones were obtained with improved selectivity.The photoprocess was facilitated by addition of pyridine or hydrogen and retarded in presence of amines or phosphines.Mechanistic interpretations for the process and the accompanying effects are discussed.Key words: chelative carbonylation, photocarbonylation, carbonylation of olefins, lactones synthesis from alkenylalcohols.
- Chow, Yuan L.,Huang, Yu-Jin,Dragojlovic, Veljko
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p. 740 - 742
(2007/10/02)
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- A convenient synthesis of 1-oxaspiro[5.5]undecane derivatives
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2-Hydroxy-1-oxaspiro[5.5]undec-3-en-5-one, which is derived from 1-(2-furyl)cyclohexan-1-ol, is used in a convenient synthesis of several 1-oxaspiro[5.5]undecane derivatives.
- Georgiadis,Tsekouras,Kotretsou,Haroutounian,Polissiou
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p. 929 - 932
(2007/10/02)
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- DIRECT SYNTHESIS OF δ-LACTONES FROM 2-(3-LITHIOPROPYL)-1,3-DIOXOLANE AND CARBONYL COMPOUNDS
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The reaction of 2-(3-lithiopropyl)-1,3-dioxolane (2), prepared in situ by lithiation of the chloroacetal 1 with lithium naphthalenide at -78 deg C, with aldehydes and ketones followed by hydrolysis with hydrochloric acid and final oxidation with PCC or Jones reagent yields the corresponding δ-lactones 5.
- Ramon, Diego J.,Yus, Miguel
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p. 3767 - 3770
(2007/10/02)
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- The Key Role of Water in the Heterogeneous Permanganate Oxidation of ω-Hydroxy Alkenes
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Potassium permanganate-copper sulphate in dichloromethane in the presence of a catalytic amount of water effects a smooth oxidative cyclization of ω-hydroxy alkenes to ω-lactones in good yields with the net loss of one or more carbon atoms in the procees.
- Baskaran, Sundarababu,Islam, Imadul,Vankar, Padma S.,Chandrasekaran, Srinivasan
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p. 1670 - 1671
(2007/10/02)
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- SUBSTITUENT DIRECTED OXIDATIVE CYCLIZATION WITH CETYLTRIMETHYLAMMONIUM PERMANGANATE: A GENERAL APPROACH TO THE SYNTHESIS OF γ- AND δ-LACTONES
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Treatment of primary, secondary or tertiary γ- and δ-hydroxyolefins with cetyltrimethylammonium permanganate gives good yields of γ- and δ-lactones by oxidative cyclization, with loss of one carbon.
- Rathore, Rajendra,Vankar, Padma S.,Chandrasekaran, S.
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p. 4079 - 4082
(2007/10/02)
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- A HIGHLY EFFICIENT SYNTHESIS OF γ- AND δ-LACTONES BY OXIDATIVE CYCLIZATION
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Treatment of tertiary γ- and δ-hydroxyolefins with pentavalent chromium reagent, (BipyH2)CrOCl5, give good yields of γ- and δ-lactones by oxidative cyclization, with loss of one carbon.Pyridinium chlorochromate (PCC) also effect this transformation to γ-lactones in reasonable yields.
- Chakraborty, T. K.,Chandrasekaran, S.
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p. 551 - 554
(2007/10/02)
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- Substituent-directed oxidation: a simple preparation of γ and δ-lactones by oxidative cyclization of hydroxyalkenes.
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Treatment of tertiary γ- and δ-hydroxyalkenes with chromium trioxide in acetic acid/acetic anhydride gives reasonable yields of γ- and δ-lactones by oxidative cyclization, with loss of one carbon. A mechanism is proposed involving formation of a chromate monoester, followed by intramolecular oxidative attack on the alkene.
- Schlecht, Matthew F.,Kim, Ho-jin
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p. 127 - 130
(2007/10/02)
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- A NEW SYNTHESIS OF δ-LACTONES FROM OXETANES
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Oxetanes were reacted with lithium enolates generated from esters or amides in the presence of boron trifluoride etherate to give δ-hydroxyesters or amides in high yield, which were hydrolyzed and converted to δ-lactones.
- Yamaguchi, Masahiko,Shibato, Keisuke,Hirao, Ichiro
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p. 1159 - 1162
(2007/10/02)
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- One-Step Spiroannelation. Synthesis of Spiro γ- and δ-Lactones
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Carbocyclic acid anhydrides can be converted to spiro γ- and δ-lactones by addition of di-Grignard reagents in tetrahydrofuran solution.Five- and six-membered rings have been formed in one-step reactions.Possible mechanistic pathways for this reaction are discussed.The conversion of spirolactones to 1-(ω-hydroxyalkyl)cycloalkanols was accomplished by reduction with LAH to illustrate the versatility of these substances giving (after or upon treatment with tosyl chloride) the corresponding spiroethers.
- Canonne, Persephone,Belanger, Denis,Lemay, Gilles,Foscolos, Georges B.
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p. 3091 - 3097
(2007/10/02)
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- One-Step Annelation. A Convenient Method for the Preparation of Diols, Spirolactones, and Spiroethers from Lactones
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1-(ω-Hydroxyalkyl)cyclopentanols and -cyclohexanols were prepared in one step in high yields from butane-1,4-diyl- and pentane-1,5-diylmagnesium dibromides and lactones in tetrahydrofuran.This method was found to be general and applicable to lactones of any size (β, γ, δ, and ε) and structure whether aliphatic, aromatic, bicyclic, or spirocyclic.Evidently important steric hindrance close to the carbonyl group prevents annelation and attack on the second nucleophilic center of the Grignard reagent.Furthermore, in the case of oxetan-2-one one obtains, in additionto the corresponding diol, products resulting from scission of the C-O bond.The diols by appropriate transformation afford new routes to spirolactones and spiroethers.
- Canonne, Persephone,Foscolos, Georges B.,Belanger, Denis
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p. 1828 - 1835
(2007/10/02)
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- Reaction of Di(bromomagnesio)alkanes with Cyclic Dicarboxylic Acid Anhydrides
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The reaction of the di(bromomagnesio)alkanes BrMg4MgBr and BrMg5MgBr with cyclic anhydrides produces spirolactones in one step in good yield.
- Canonne, Persephone,Belanger, Denis
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p. 125 - 126
(2007/10/02)
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