- Asymmetric synthesis of the tricyclic core of calyciphylline A-type alkaloids via intramolecular [3 + 2] cycloaddition
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Asymmetric synthesis of the [5-6-7] tricyclic system common to the Calyciphylline A-type alkaloids is reported, featuring Overman rearrangement, Heck cyclization, intramolecular [3 + 2] cycloaddition, diastereoselective hydrogenation, and Claisen rearrangement as strategic events. The approach is capable of installing the crucial carbonyl functionality as well as multiple stereogenic centers within a congested polycyclic ring skeleton.
- Wang, Lu,Xu, Chen,Chen, Li,Hao, Xiaojiang,Wang, David Zhigang
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supporting information
p. 1076 - 1079
(2014/03/21)
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- Rapid construction of [5-6-7] tricyclic ring skeleton of calyciphylline alkaloid daphnilongeranin B
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A concise photochemical [2 + 2] cycloaddition-Grob fragmentation sequence sets the common tricyclic ring skeletons of the Calyciphylline A-type alkaloids, particularly those in daphnilongeranins, daphniyunnines, and daphniglaucins.
- Xu, Chen,Liu, Zheng,Wang, Huifei,Zhang, Bo,Xiang, Zheng,Hao, Xiaojiang,Wang, David Zhigang
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supporting information; experimental part
p. 1812 - 1815
(2011/06/19)
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- Mitsunobu Reaction of Unbiased Cyclic Allylic Alcohols
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The stereochemical inversion of unbiased allylic alcohols using triphenylphosphine, diethyl azodicarboxylate, and benzoic acid, commonly known as the Mitsunobu reaction, was studied in three different solvents with specific attention toward the product composition. The results generated for the Mitsunobu reaction of (R)-3-deuterio-2-cyclohexen-1-ol and the cis and trans isomers of 1-deuterio-5-methyl-2-cyclohexen-1-ol, 1-deuterio-5-tert-butyl-2-cyclohexen-1-ol, and optically active cis and trans 5-isopropyl-2-methyl-2-cyclohexen-1-ol all gave similar product distributions with respect to inversion and retention at the carbinol center as well-as syn and anti Sn2′ type addition when THF or benzene was used as the solvent (CH2Cl2 gave less selective product distributions). Interestingly, it was found that the quasi-equatorial and quasi-axial nature of the starting allylic alcohol does not appear to affect the product distribution for this reaction, nor does methyl substitution at the central carbon of the allylic alcohol. In all cases, significant amounts (8-28%) of non-SN2 type products were detected for these sterically unbiased allylic alcohols; only 72-77% of the product was from SN2 type reaction when sterically undemanding (R)-S-deuterio-2-cyclohexen-1-ol was subjected to Mitsunobu conditions.
- Shull, Brian K.,Sakai, Takashi,Nichols, Jeffrey B.,Koreeda, Masato
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p. 8294 - 8303
(2007/10/03)
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- Synthesis of Alkyl Allylic Ethers and 1,3-Dienes by the Reaction of Conjugated Cyclohexenones with Sodium Borohydride-Cerium(III) Chloride in Aliphatic Alcohols
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The reaction of conjugated cyclohexenones 1,3-containing 3-methyl-2-en-1-one moiety with NaBH4/CeCl3*7H2O in primary aliphatic alcohols (MeOH, EtOH, n-PrOH) affords alkyl allylic ethers and 1,3-dienes.In isopropanol or tert-butanol only 1,3-dienes are obtained.Ketones 4-6 containing 2-methyl-2-en-1-one moiety are reduced under the same conditions to the corresponding allylic alcohols irrespective of the alcohol used.Key words: reduction, α,β-unsaturated ketones, allylic alcohols, alkyl allylic ethers, sodium borohydride, cerium(III) chloride
- Uzarewicz, A.,Dresler, R.
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p. 1655 - 1658
(2007/10/03)
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- LIGHT-MEDIATED TRANSFORMATIONS OF OLEFINS INTO ALCOHOLS: REACTIONS OF HYDROXYL RADICALS WITH CYCLOALKENES
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Reactions of hydroxyl radicals, generated by photodecomposition of hydrogen peroxide in acetonitrile, with a wide variety of cycloalkenes have been examined.The results show that the major reaction is the addition of hydroxyl radicals to the less substituted end of the double bond, furnishing the secondary alcohols.The reactivity pattern and the observed regio- and stereoselectivity clearly reveal that the steric parameters associated with the substrates play a dominant role in directing the addition reactions.More importantly, this study led to the development of a new methodology for the facile conversions of olefins essentially into secondary alcohols, and includes a few examples which demonstrate the potential of the method.
- Sonawane, H. R.,Nanjundiah, B. S.,Kelkar, R. G.
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p. 6673 - 6682
(2007/10/02)
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- Carvone- and Piperitone-Derived Allylic Stannanes and Aspects of Their Electrophilic Substitution
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cis- and trans-Carvotanacetols and -piperitols have been converted into the corresponding allylic chlorides, which were made to react with both trimethyltinlithium and triphenyltinlithium.The resulting allylic stannanes were characterized by 1H, 13C and 119Sn n.m.r. spectroscopy, which permitted assignment of the relative configurations.Triphenyltinlithium appears to react in a (substantially) concerted fashion with the (optically active) chloride from the carvotanacetols yielding an optically active stannane.The corresponding trimethylstannane is optically inactive.Substitution reactions (SE') with acid and sulfur dioxide (in chloroform) are preferentially γ-anti and specifically γ-syn respectively, in line with conclusions based on other cyclohex-2-enyl systems.
- Young, David,Jones, Martin,Kitching, William
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p. 563 - 573
(2007/10/02)
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