36613-11-3Relevant articles and documents
Cyclopentyl and carbohydrate derivatives of N-hydroxy-4-methylthiazole-2(3H)-thione: Synthesis by Mitsunobu reaction and highly selective photochemical conversion into aldehydes
Hartung,Gottwald,Kneuer
, p. 749 - 752 (2001)
Substituted N-cyclopentoxy- and carbohydrate-derived thiazole-2(3H)-thiones 3 were prepared from alcohols 2 or from 2,3:5,6-di-O-isopropylidene mannose in the presence of PPh 3, diethyl azodicarboxylate (DEAD), and N-hydroxy-4-methylthiazole-2(3H)-thione (1). Alkoxyl radical precursors 3 were photoreacted with hydrogen atom donors to afford substituted aldehydes 7 or formyl esters 10-11 via highly regioselective alkoxyl radical fragmentations.
Controlled Reduction of Nitriles by Sodium Hydride and Zinc Chloride
Chiba, Shunsuke,Ong, Derek Yiren
, p. 1369 - 1378 (2020/04/27)
A new protocol for the controlled reduction of nitriles to aldehydes was developed using a combination of sodium hydride and zinc chloride. The iminyl zinc intermediates derived from aromatic nitriles could be further functionalized with allylmetal nucleophiles to afford homoallylamines. As the method allows the reduction of various aliphatic and aromatic nitriles with a concise procedure under milder reaction conditions and exhibits wide functional group compatibility, it is well suited for use in various opportunities in chemical synthesis.
Reduction of N,N-Dimethylcarboxamides to Aldehydes by Sodium Hydride–Iodide Composite
Chan, Guo Hao,Ong, Derek Yiren,Yen, Zhihao,Chiba, Shunsuke
, (2018/05/14)
A new and concise protocol for selective reduction of N,N-dimethylamides into aldehydes was established using sodium hydride (NaH) in the presence of sodium iodide (NaI) under mild reaction conditions. The present protocol with the NaH-NaI composite allows for reduction of not only aromatic and heteroaromatic but also aliphatic N,N-dimethylamides with wide substituent compatibility. Retention of α-chirality in the reduction of α-enantioriched amides was accomplished. Use of sodium deuteride (NaD) offers a new step-economical alternative to prepare deuterated aldehydes with high deuterium incorporation rate. The NaH-NaI composite exhibits unique chemoselectivity for reduction of N,N-dimethylamides over ketones.
Solvolysis of 2,2-dialkylvinyl iodonium salt: Alkyl participation and possibility of a primary vinylic cation intermediate
Okuyama, Tadashi,Yamataka, Hiroshi,Ochiai, Masahito
, p. 2761 - 2769 (2007/10/03)
Solvolysis of (E)- and (Z)-2-methyl-5-phenyl-1-pentenyl(phenyl)iodonium tetrafiuoroborate (1·BF4) was carried out in various alcohols, acetic acid, and aqueous solutions at 60 °C. Products (after acid hydrolysis) include iodobenzene and 2-methyl-5-phenylpentanal as well as rearranged ones: 6- phenyl-2-hexanone, 6-phenyl-3-hexanone, 6-phenyl-2-hexyne, 6-phenyl- 1,2- hexadiene, and 6-phenyl-2,3-hexadiene. The products of α-elimination, including 1-methyl-3-phenyl-1-cyclopentene, were also obtained in methanol and ethanol. Solvolysis of the E isomer (E)-1 is faster than that of (Z)-1 in every solvent examined. The percentage of rearrangement is higher with (E)-1 than with (Z)-1, and the main rearranged products are those of migration of the alkyl group trans to the iodonio group, but migration of the cis alkyl group is also involved. Theoretical calculations suggest that interconversion between the secondary Vinylic cations by 1,2-hydride shift is rapid. These results show that a major heterolysis reaction occurs with β-alkyl participation to directly give a secondary vinylic cation, but stereochemistry of the unrearranged substitution products suggests that formation of the primary vinylic cation is also involved in less nucleophilic solvents like acetic acid and 2,2,2-trifluoroethanol.
Solvolysis of β,β-dialkylvinyliodonium salt: Primary vinyl cation intermediate and alkyl participation
Okuyama, Tadashi,Sato, Koichi,Ochiai, Masahito
, p. 1177 - 1178 (2007/10/03)
Solvolysis of both E and Z isomers of a β,β-dialkylvinyl-(phenyl)iodonium salt gave extensively rearranged products. A mechanism involving a primary vinyl cation intermediate as well as the alkyl participation leading to secondary vinyl cations is proposed.
Stereocontrolled synthesis of E-homoallylic sulfides with 1,4,5 related chiral centres using the [2,3] sigmatropic rearrangement of sulfonium ylides
Hartley, Richard C.,Richards, Ian C.,Warren, Stuart
, p. 359 - 376 (2007/10/03)
E-Homoallylic sulfides with 1,4,5 related chiral centres have been synthesised in a stereocontrolled way. An aldol condensation sets up the stereochemistry. Lactonisation with 1,2 arylsulfanyl migration followed by reduction and sulfur-assisted dehydratio
Cob(I)alamin als Katalysator. 6. Mitteilung . Bildung und Fragmentierung von Alkylcobalaminen, ein Gleichgewichtsprozess zwischen nukleophiler Addition und reduktiver Fragmentierung
Fischli, Albert,Mueller, Peter Michael
, p. 529 - 554 (2007/10/02)
Isolated olefines can be saturated using catalytic amounts of cob(I)alamin in aqueous acetic acid; as electron source an excess of zinc dust is added to the solution containing the homogeneous catalyst.During this overall hydrogenation of isolated double bonds intermediate alkylcobalamins are formed (compare e.g.Schemes 2, 4, 5, 7 and 12).Clear evidence is presented that the nucleophilic attack on the isolated double bond is carried out by cob(I)alamin and not by cob(II)alamin also present in the system (see Scheme 3b and 3c).As this catalytic saturation of olefins depends on the pH of the solution, characterized by a slow reaction at pH=7.0 compared to the same reduction in aqueous acetic acid (see Scheme 2, 2 -> 4, and Scheme 3a), it is reasonable to accept the participation of an electrophilic attack by a proton during the generation of alkylcobalamins. - We use the term nucleophilic addition to describe the formation of alkylcobalamins from a proton, an olefin and cob(I)alamin (compare Schemes 4-7 and 12).A special sequence of experiments showed the nucleophilic addition to beregioselective.Preferentially the higher substituted alkylcobalamin revealed to be produced.Therefore, the nucleophilic addition of cob(I)alamin follows the Markownikoff rule (compare chap. 4: formation and fragmentation of β-hydroxyalkylcobalamins).Under the reaction conditions applied the intermediate alkylcobalamins can be present in base-on and base-off forms.They are known to exist as octahedral complexes and might also be stable to some extent as tetragonal-pyramidal species.In addition the base-off forms can partially be protonated at the dimethylbenzimidazole moiety in aqueous acetic acid (compare Scheme 12).From this equilibrium of intermediate alkylcobalamins three modes of decay disclosed to be possible: (i) The reductive fragmentation leading to an olefin, a proton, and cob(I)alamin is the formal retro-reaction of the nucleophilic addition (see Schemes 2, 4 and 6-12).This equilibrium of an associated alkylcobalamin and the corresponding dissociation products revealed to be a fast process compared to the reductive cleavage of the Co, C-bond cited below (s. (iii)). (ii) As the second reaction pattern an oxidative fragmentation producing an olefin, a hydroxy anion (or water, respectively) and cob(III)alamin has been observed (see Schemes 7, 8, 10 and 12). (iii) The slow reductive cleavage of the Co, C-bond, initiated by addition of electrons (see ), was the third reaction path observed (see Schemes 2, 4-8 and 10-12. - The stereochemistry of the three transformations originating from the intermediate alkylcobalamins is unknown up to now.The antiperiplanar pattern of the fragmentation reactions presented in the Schemes has been chosen arbitrarily (see e.g.Scheme 12).
