Seven-membered rings via silyl enol ether participation in the olefin cyclization. Anti-Markownikoff cyclization in biomimetic terpene synthesis

Hashimoto, Shinsuke; Itoh, Akira; Kitagawa, Yuuki; Yamamoto, Hisashi; Nozaki, Hitosi

doi:10.1021/ja00454a066

Cited by 57 publications

(7 citation statements)

References 4 publications

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“…Next, group 13 metals, such as AlCl 3 and GaCl 3 , were employed for the reaction; however, only moderate conversions of 1a were observed ( entries 3 and 4 ). TiCl 4 , which was used in intramolecular allylic alkylations, [23] showed moderate activity to give the allylated product 2a and its isomer 3a in 56 % yield with 2a / 3a 85 : 15 ( entry 5 ). When the catalysts of group 4 were investigated, it was found that ZrCl 4 could efficiently convert 1a into 2a and 3a in 80 % yield with the regioselectivity of 2a / 3a 70 : 30 ( entry 6 ).…”

Section: Resultsmentioning

confidence: 99%

“…At first, this allylic alkylation was reported as an intramolecular reaction by the Nozaki group. [23] An allylic acetate bearing a silyl enol ether was treated by a catalytic amount of MeAl(OCOCF 3 ) 2 to give a seven-membered homoallylic ketone. This methodology was applied to an intermolecular reaction by Saigo et al (Scheme 1,c).…”

Section: Introductionmentioning

confidence: 99%

“…An acid‐catalyzed allylic alkylation of allyl acetate also affords the corresponding homoallylic ketone. At first, this allylic alkylation was reported as an intramolecular reaction by the Nozaki group [23] . An allylic acetate bearing a silyl enol ether was treated by a catalytic amount of MeAl(OCOCF 3 ) 2 to give a seven‐membered homoallylic ketone.…”

Section: Introductionmentioning

confidence: 99%

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Lewis Acid‐Mediated Decarboxylative Allylation of Enol Carbonates

Dokai

Nishizawa

Saito

et al. 2021

Helvetica Chimica Acta

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Dedicated to Prof. Peter Kündig on the occasion of his 75th birthday A homoallylic ketone can be transformed and functionalized by various synthetic reactions, and thus, is regarded as one of the representative building blocks in organic chemistry. An additional route to access homoallylic ketones, namely, a Lewis acid-mediated decarboxylative allylation of cyclic enol carbonates, prepared by fixation of carbon dioxide onto propargyl alcohols, was developed in this work. The treatment of a cyclic enol carbonate with a Lewis acid in the presence of an allylsilane resulted in the formation of a homoallylic ketone. It was found that the title reaction proceeded well by the combined use of zirconium tetrachloride with allyltrimethylsilane. The allylation occurred with high regioselectivity and the corresponding homoallylic ketones were obtained in good-to-high yields. A reaction mechanism involving the decarboxylative formation of an oxyallyl cation equivalent is proposed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Lewis Acid‐Mediated Decarboxylative Allylation of Enol Carbonates

Dokai

Nishizawa

Saito

et al. 2021

Helvetica Chimica Acta

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“…Thus, upon treatment with methylaluminum bis(trifluoroacetate) in dichloromethane (10 min at 0°C and 3 h at 25°C) we obtained karahanaenone in 95% yield [23]. Reaction of ( 4 6 ) with trimethylaluminum resulted in formation of the C-methylated cyclic silyl ether ( 4 7 ) .…”

Section: (34)mentioning

confidence: 97%

Selective Reactions with Organoaluminum Compounds

Yamamoto

Nozaki

1978

Angew. Chem. Int. Ed. Engl.

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With the aid of selected examples an overview is given of the development trends in highly discriminative reactions using organoaluminum compounds. 1) Isomerization of substituted oxiranes into allyl alcohols has been effected both stereo-and regioselectively by means of a new organoaluminum reagent, diethylaluminum 2,2,6,6-tetramethylpiperidide (DATMP); this reaction which provides a new route for the regiospecific transformation of allyl alcohols into 1,3-dienes. 2) A novel nonenzymic heterolysis of allylic phosphates of terpenoids has been effected by organoaluminum compounds and has enabled development of a new method for the selective synthesis of cyclic terpenes.3) The reductive condensation of a-haloketones with carbonyl compounds in the presence of diethylaluminum chloride and zinc affords 8-hydroxycarbonyl derivatives in good yields with exclusion of undesired self-condensations products.

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“…The next step, conversion of the α-iodo ketones 7 to the corresponding enolates 8 , was explored first with 7a as a representative case under the conditions of Borowitz ((EtO) 3 P in EtOH or CHCl 3 ; Ph 2 POMe in CHCl 3 ), − Utimoto (EtMgBr in Et 2 O; Et 3 B in Et 2 O or PhH), , and Joshi (Zn/TMSCl/THF) . Among these protocols, use of EtMgBr was successful to generate the corresponding enolate 8a from iodide 7a , and reaction of enolate 8a and (EtO) 2 P(O)Cl afforded the enol phosphate 4a in 71% yield (Scheme and entry 1 of Table ).…”

mentioning

confidence: 99%

A Method To Accomplish a 1,4-Addition Reaction of Bulky Nucleophiles to Enones and Subsequent Formation of Reactive Enolates

William

Kobayashi

2001

Org. Lett.

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[reaction: see text] BF(3)-promoted 1,4-addition of bulky aryl groups to alpha-iodo enones, prepared from the parent enones, afforded beta-aryl-alpha-iodo ketones. Subsequent reaction with EtMgBr furnished the magnesium enolates, which upon reactions with ClP(O)(OEt)(2) and aldehydes gave enol phosphates and aldols, respectively. This method was applied successfully to a synthesis of Delta(1)-trans-tetrahydrocannabinol.

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Seven-membered rings via silyl enol ether participation in the olefin cyclization. Anti-Markownikoff cyclization in biomimetic terpene synthesis

Cited by 57 publications

References 4 publications

Lewis Acid‐Mediated Decarboxylative Allylation of Enol Carbonates

Lewis Acid‐Mediated Decarboxylative Allylation of Enol Carbonates

Selective Reactions with Organoaluminum Compounds

A Method To Accomplish a 1,4-Addition Reaction of Bulky Nucleophiles to Enones and Subsequent Formation of Reactive Enolates

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