- HFIP Solvent Enables Alcohols to Act as Alkylating Agents in Stereoselective Heterocyclization
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A new method for the stereoselective synthesis of highly functionalized oxygen heterocycles using allyl or benzyl alcohols as alkylating agents is presented. The process is efficient and atom economic, generating water as the only stoichiometric byproduct. Substoichiometric amounts of Ti(OiPr)4 in HFIP solvent are key to this reactivity, and the method tolerates a broad substitution pattern on both the alcohol initiator and homoallylic alcohol substrate. Preliminary mechanistic studies reveal in situ formation of a titanium complex with HFIP which may initiate the cyclization reaction. Further stereoselective functionalization of the products allows access to a diverse range of interesting heterocyclic structures.
- Zhu, Yuxiang,Colomer, Ignacio,Thompson, Amber L.,Donohoe, Timothy J.
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p. 6489 - 6493
(2019/05/06)
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- NHC-Copper-Catalyzed Tandem Hydrocupration and Allylation of Alkenyl Boronates
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A tandem hydrocupration/allylation of alkenyl boronates efficiently proceeds with NHC-copper catalysts using hydrosilane and allyl phosphate as reagents. In the presence of IMes-Cu catalyst, the allylation of in situ generated Β-α-copper intermediates smoothly occurs to give homoallylic boronates in high yields, despite competitive side reaction pathways. Mono- and disubstituted alkenyl boronates were effective in the reaction with terminal allyl phosphates, but trisubstituted substrates showed limited reactivity.
- Jang, Won Jun,Han, Jung Tae,Yun, Jaesook
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supporting information
p. 4753 - 4758
(2017/10/27)
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- Iridium-Catalyzed coupling reaction of primary alcohols with 2-alkynes leading to hydroacylation products
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A novel iridium-catalyzed intermolecular coupling reaction of primary alcohols or aldehydes with 2-alkynes was successfully achieved with high regioselectivity to give hydroacylation products such as α,β- unsaturated ketones in good yields. The mechanistic investigation of the reaction strongly indicated that the coupling proceeds through the initial formation of homoallylic alcohols followed by dehydrogenation to β,γ-unsatutated ketones and then isomerisation, which leads to the hydroacylation products.
- Hatanaka, Shintaro,Obora, Yasushi,Ishii, Yasutaka
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experimental part
p. 1883 - 1888
(2010/06/20)
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- Iridium-catalyzed coupling reaction of primary alcohols with 1-aryl-1-propynes leading to secondary homoallylic alcohols
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We report iridium-catalyzed coupling of 2-alkynes such as 1-aryl-1-propynes with primary alcohols leading to secondary homoallylic alcohols as products. This reaction involves an iridium-catalyzed novel catalytic transformation of 2-alkynes and primary al
- Obora, Yasushi,Hatanaka, Shintaro,Ishii, Yasutaka
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supporting information; experimental part
p. 3510 - 3513
(2009/12/25)
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- Reductive cleavage of 2-methyleneoxetanes with lithium and 4,4'-di-tert- butylbiphenyl
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3,3-Dimethyl-2-mcthylene-4-phenyloxetane (5) undergoes reductive cleavage with lithium and 4,4'-di-tertbutylbiphenyl (DTBB) to give an intermediate dianion, which reacts regioselectively with aldehydes and ketones to give aldol adducts in modest yields. A
- Hashemzadeh, Mehrnoosh,Howell, Amy R.
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p. 1855 - 1858
(2007/10/03)
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- Hydroboration of mono-substituted allenes: A general synthetic route to the higher crotylboranes and anti-3-alkyl/aryl-4-hydroxy-1-alkenes
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Hydroboration of mono-substituted allenes with Chx2BH at 0°C leads to the corresponding (E)-substituted allylboranes, known as higher crotylboranes, exclusively. These higher crotylboranes react with aldehydes, and on oxidation, provide the cor
- Narla, Gowriswari,Brown, Herbert C.
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p. 219 - 222
(2007/10/03)
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- Benzotriazole-mediated [2,3]-wittig rearrangement. General and stereocontrolled syntheses of homoallyl alcohols and β,γ-unsaturated ketones
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Readily accessible allyl 1-(benzotriazol-1-yl)alkyl ethers (13 and 19), upon treatment with 2.5 equiv of nucleophilic lithium reagents, give secondary and tertiary homoallyl alcohols (16 and 21), respectively, exclusively in the E configuration in excellent yields. This is achieved by deprotonation followed by [2,3]-Wittig rearrangement, departure of the benzotriazolyl group, and then nucleophilic addition to the resulting carbonyl compound. Following a similar protocol, primary E-homoallyl alcohols 18 are prepared in good yield by the reaction of ethers 13 with LDA in the presence of NaBH4. Our approach complements the stereochemical Z-selective syntheses of primary homoallyl alcohols of Still and of Bruckner. Wittig rearrangement of the anions of 19 generated with LDA analogously furnishes E-β,γ-unsaturated ketones 20 in excellent yields.
- Katritzky, Alan R.,Wu, Hong,Xie, Linghong
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p. 4035 - 4039
(2007/10/03)
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- Reinvestigation of the Lewis Acid-mediated Reaction of 3-Aryl-substituted Allyltin Reagents toward Aldehydes. Divergent Stereocontrol of the Product by Lewis Acids
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3-Arylallyltin reagents including cinnamyltin stereoselectively gave anti-adducts in the ZnCl2-mediated reaction toward aldehydes in a donating solvent via the 6-membered cyclic transition state.In contrast, the BF3-mediated reaction gave syn-adducts via
- Nishigaichi, Yutaka,Takuwa, Akio
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p. 1429 - 1432
(2007/10/02)
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- Stereoselective synthesis of allylic boronates via palladium-catalyzed cross-coupling reaction of Knochel's (dialkoxyboryl)methylzinc reagents with 1-halo-1-alkenes
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The cross-coupling reaction of (dialkoxyboryl)methylzinc regents IZnCH2B(OR)2 with 1-halo-1-alkenes was catalyzed by triphenylphosphine- or triphenylarsine-based palladium complexes to provide esters of stereodefined allylboronic acids with stereoselectiv
- Watanabe, Takeo,Miyaura, Norio,Suzuki, Akira
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- Palladium-catalyzed carbonyl allylation by allylic alcohols with SnCl2
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Allylic alcohols can be applied to carbonyl allylation via the formation of π-allylpalladium complexes, using palladium as catalyst and SnCl2 as a reducing agent. This reaction has chemoselectivity: The reactivity order of allylating agents is allylic carbonate > allylic alcohol > allylic acetate, and that of carbonyl compounds is aldehyde > ketone. High regioselcction was observed in polar solvents such as DMF, DMI, and DMSO; carbonyl compounds apparently attacked the more substituted allylic position of π-allylpalladium complexes to afford only one regioisomer. Diastereocontrol in the carbonyl allylation of aromatic aldehydes by (E)-2-butenol was achieved by the choice of polar solvents; use of DMSO at 25 °C led to syn selection, while anti selection was found at -10 °C in THF. The addition of H2O in any solvent accelerated the carbonyl allylation and enhanced both regioselectivity and the diastereoselectivity. Anti selection in DMF, DMI, and THF-H2O can be explained by the chair form of the six-membered cyclic transition state, while syn selection in DMSO allows us to propose an acyclic antiperiplanar transition state. An NMR spectroscope investigation demonstrated that the actual allylating agent in dry medium was allyltrichlorotin: 1H, 13C, and 119Sn NMR spectra of the reaction of allyl alcohol with PdCl2(PhCN)2-SnCl2 in DMF-d7. corresponded to those of the reaction of allyl chloride with PdCl2(PhCN)2-SnCl2 in DMF-d7.
- Takahara, Jun P.,Masuyama, Yoshiro,Kurusu, Yasuhiko
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p. 2577 - 2586
(2007/10/02)
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- DIASTEREOSELECTIVITY, DIASTEREOFACIAL SELECTIVITY AND REGIOSELECTIVITY IN THE REACTIONS OF CYNNAMYL CHLORIDE WITH ALDEHYDES MEDIATED BY TIN AND ALUMINIUM
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The reaction of cinnamyl chlorie with a series of aryl and alkyl aldehydes mediated by tin and aluminium has been shown to be regioselective and threo diastereoselective.For aldehydes with chirality adjacent to the carbonyl function some diastereofacial s
- Coxon, James M.,Eyk, Stephen J. van,Steel, Peter J.
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p. 1029 - 1042
(2007/10/02)
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- HIGHLY DIASTEREOSELECTIVE REACTIONS OF (E)-CINNAMYL CHLORIDE WITH ALDEHYDES MEDIATED BY TIN AND ALUMINIUM
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The reactions of (E)-cinnamyl chloride with aldehydes in H2O:THF:HBr in the presence of tin and aluminium powders proceed with very high stereoselectivity.
- Coxon, James M.,Eyk, Stephen J. van,Steel, Peter J.
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p. 6121 - 6124
(2007/10/02)
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- ERYTHROSELECTIVITY IN ADDITION OF γ-SUBSTITUTED ALLYLSILANES TO ALDEHYDES IN THE PRESENCE OF TITANIUM CHLORIDE
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(E)-Crotyltrimethylsilane and (E)-cinnamyltrimethylsilane were allowed to react with aldehydes (RCHO: t-Bu, i-Pr, Et, Me) in the presence of titanium chloride to give erythro homoallyl alcohols with over 93percent selectivity.Lower erythroselectivity was observed in the reaction of (Z)-allylsilanes.
- Hayashi, Tamio,Kabeta, Keiji,Hamachi,Itaru,Kumada, Makoto
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p. 2865 - 2868
(2007/10/02)
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- STEREOSELECTIVE ACYCLIC SYNTHESIS VIA ALLYLMETALS: STRUCTURAL DEPENDENCE IN A LEWIS-ACID CATALYZED ADDITION OF ALLYLTINS TO ALDEHYDES
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Lewis-acid catalyzed reaction of allyltins with aldehydes at -78 deg C provide homoallyl alcohols with high stereoselectivity; 2-alkenyltins in general provide erythro adducts preferentially with an erithro/threo ratio greater than 12/1, whereas only thre
- Koreeda, Masato,Tanaka, Yoshio
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p. 1299 - 1302
(2007/10/02)
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- HOMOLYTIC DISPLACEMENT AT CARBON. V. FORMATION OF CYCLOPROPYLCARBINYLSULPHONES AND TRICHLOROETHYLCYCLOPROPANES FROM BUT-3-ENYL COBALOXIMES BY A NOVEL PROCESS INVOLVING HOMOLYTIC ATTACK AT THE δ-CARBON OF THE BUTENYL LIGAND
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But-3-enyl- and substituted but-3-enylcobaloximes react with bromotrichlormethane (or trichloromethanesulphonyl chloride) and with 4-toluenesulphonyl chloride thermally or photochemically to give good yields of β,β,β-trichloroethylcyclopropanes and cyclopropylcarbinyl(tolyl)sulphones, respectively.The reactions proceed by a chain mechanism in which a key step is a novel process in which homolytic attack of a trichloromethyl or 4-toluenesulphonyl radical at the δ-carbon of the butenyl ligand leads to synchronous or subsequent attack of the incipient γ-carbon radical on the α-carbon, causing cyclisation and displacement of cobaloxime(II).The other propagation step involves the reaction of the cobaloxime(II) with the bromotrichloromethane, trichloromethanesulphonyl chloride or 4-toluenesulphonyl chloride to give the reactive organic radical.
- Ashcroft, Martyn R.,Bury, Adrian,Cooksey, Christopher J.,Davies, Alwyn G.,Gupta, B. Dass,et al.
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