- OZONOLYTIC CLEAVAGE OF CYCLOALKENES TO TERMINALLY DIFFERENTIATED PRODUCTS
-
Conditions are reported which convert cycloalkenes to terminally differentiated product through the intermediacy of α-alkoxy hydroperoxides.
- Schreiber, Stuart L.,Claus, Ronald E.,Reagan, Jeff
-
-
Read Online
- MECHANISTIC AND SYNTHETIC ASPECTS OF THE ACID-CATALYSED HYDROLYSIS OF 2,2-DIMETHOXY-3,4-DIHYDROPYRANS INTO 3,4-DIHYDRO-α-PYRONES AND δ-KETO ESTERS
-
Acid-catalysed hydrolysis of 2,2-dimethoxy-3,4-dihydropyrans (1) yields mixtures of δ-keto esters (2) and 3,4-dihydro-α-pyrones (3).The amount of 3 increases with increasing alkyl substitution in the 3-, 5- and 6-position of 1 and when the hydrolysis is carried out in a two-phases system of water/dichloromethane.It is shown that 3 is formed directly from 1 whereas 2 is formed directly from 1 and by methanolysis of 3.The mechanistic and synthetic aspects of these hydrolysis reactions are discussed.
- Scheeren, J. W.,Bakker, C. G.,Peperzak, R.,Nivard, R. J. F.
-
-
Read Online
- Ozonolysis of 3-caren-5-one
-
Cleavage by ozonolysis of a cyclic unsaturated ketone, 3-caren-5-one, was investigated under different conditions. The main reaction product is ketocaronic acid. A scheme of ketocaronic acid formation was suggested basing on kinetics of ozone reaction with 3-caren-5-one and thermal decomposition of peroxides.
- Galin,Kukovinets,Zainullin,Shershovets,Kashina,Akhmetov,Kunakova,Tolstikov
-
-
Read Online
- Oxidation of 2-substituted cycloalkanones with cerium(IV) sulfate tetrahydrate in alcohols and acetic acid
-
The reaction of 2-substituted cycloalkanones with cerium(IV) sulfate tetrahydrate (CS) in alcohols and acetic acid gave the corresponding alkyl esters of oxo acids (80-96%) and oxo acids (78-96%), respectively, by oxidative cleavage of the C(R).C=O bond. In the case of 2-iodocycloalkanones in methanol, the dimethyl ester was obtained in good yield. A treatment of 5α-cholestan-3-one with CS in methanol produced 2-acetal 3-ester of 2,3-seco derivative in good yield. The effects of cerium(IV) and copper(II) salts are also discussed.
- He, Liangyou,Horiuchi, C. Akira
-
p. 2515 - 2521
(2007/10/03)
-
- Dehydrooligopeptides. XVI. Convenient syntheses of two kinds of antrimycins Av and Dv containing dehydrovaline residues
-
Eight kinds of peptide antibiotics, antrimycins (1), consist of four sorts of unusual α-amino acids, that is, hydroxymethylserine, (2S,3S)-2,3-diaminobutanoic acid, (S)-2,3,4,5-tetrahydro-3-pyridazinecarboxylic acid, and dehydrovaline (ΔVal) or (E)-dehydr
- Nakamura,Ito,Shin
-
p. 2151 - 2161
(2007/10/02)
-
- Useful Syntheses of (3S)-2,3,4,5-Tetrahydropyridazine-3-carboxylic Acid and Its Dehydrotetrapeptide Derivatives
-
The stereoselective synthesis of (3S)-2,3,4,5-tetrahydropyridazine-3-carboxylic acid (Pya), which is a cyclic α-amino acid at center of antrimycins (1), was successful.Moreover, the synthesis of the C-terminal dehydrotetrapeptide of 1 containing Pya residue at N-terminus is described.
- Nakamura, Yutaka,Shin, Chung-gi
-
p. 1953 - 1956
(2007/10/02)
-
- Ozonolysis of Symmetrically 1,2-Disubstituted Ethylenes in HCl/Methanol Solutions: Acid Catalyzed Reactions of Primary Cleavage Products
-
The ozonolysis of olefins in 1 M anhydrous solutions of hydrogen chloride in methanol at /= 0 deg C was investigated.Upon warm-up of the ozonolysis products, the peroxidic primary fragmentation products were converted into non peroxidic end-products by HCl-catalyzed reactions.Cyclopentene (1a) and cyclohexene (1b), e.g., afforded mixtures of the corresponding α,ω-dialdehydebis(dimethyl acetals) (8), dimethyl α,ω-dicarboxylates (9), and methyl ω-aldehyde dimethyl acetal carboxylates (10).Norbornene (1c) gave a mixture of the correspondingly substituted 1,3-cyclopentane compounds (8c - 10c), phenanthrene (22) gave a mixture of methyl 2'-formyl-2-biphenylcarboxylate (24a), 2,2'-biphenyldicarbaldehyde (24b), and dimethyl 2,2'-biphenyldicarboxylate (24c).A reaction scheme was advanced for the rationalization of the types and the distribution of the products.It was partly substantiated by model reactions.
- Griesbaum, Karl,Neumeister, Joachim
-
p. 2697 - 2706
(2007/10/02)
-