Record-Breaking Steric Crowding in Trialkylamines Prepared by Oxidative Ring Opening

Synthesis ◽  
2020 ◽  
Vol 52 (24) ◽  
pp. 3801-3810
Author(s):  
Klaus Banert ◽  
Manuel Heck ◽  
Andreas Ihle ◽  
Erik Michael ◽  
Richard Weber
Keyword(s):  
Ring Opening ◽  
Room Temperature ◽  
Osmium Tetroxide ◽  
Model Compound ◽  
Ring Cleavage ◽  
Open Chain ◽  
Tert Butyl ◽  
Steric Crowding ◽  
Acid Catalyzed ◽  
Subsequent Acid

AbstractEpoxidation of olefinic heterocyclic amines and subsequent acid-catalyzed hydrolysis or alternatively the direct dihydroxylation with the help of osmium tetroxide led to diols, which underwent ring cleavage in the presence of lead tetraacetate to give 3-isopropyl-2,2,4,4-tetramethyl-3-azahexanedial and 3-tert-butyl-2,2,4,4-tetramethyl-3-azapentanedial. Whereas the former dialdehyde is a highly unstable model compound because of a rapid intramolecular aldol reaction, the latter product proves to be isolable at room temperature. Furthermore, this compound is the first open-chain tri-tert-alkylamine establishing in a new record of steric crowding in tertiary amines. Strong tendencies to a Hofmann-like elimination reaction or to ring-closing reactions were observed when the aldehyde units of 3-tert-butyl-2,2,4,4-tetramethyl-3-azapentanedial were transformed into other functionalities, since both types of reactions led to a significantly decrease of the steric stress.

The bromination and chlorination of 2,3-dialkylindoles. Isolation of 3-bromo- and 3-chloro-2,3-dialkylindolenines and acid catalyzed conversion to 3-methoxyindolenines

1980 ◽  
Vol 58 (8) ◽  
pp. 808-814 ◽  
Author(s):  
Gary I. Dmitrienko ◽  
Edward A. Gross ◽  
Susan F. Vice
Keyword(s):  
Acetic Acid ◽  
Good Yield ◽  
Room Temperature ◽  
Chemical Properties ◽  
Nitrogen Atmosphere ◽  
Crystalline Solid ◽  
Tert Butyl ◽  
Acidic Conditions ◽  
Acid Catalyzed

The bromination of 2,3-dimethylindole in acetic acid followed by hydrolysis has been shown to yield the known dimer 16 of 3-hydroxy-2,3-dimethylindolenine 15 and not 3-hydroxymethyl-2-methylindole 12 as reported previously by others. Bromination of 2,3-dimethylindole in the presence of triethylamine has yielded 3-bromo-2,3-dimethylindolenine 17 as a crystalline solid which is stable at room temperature in a nitrogen atmosphere in the presence of triethylamine but decomposes vigorously in the absence of base. Under mildly acidic conditions 17 reacts rapidly with methanol to yield 3-methoxy-2,3-dimethylindolenine 3 in good yield. With tert-butyl hypochlorite in the presence of triethylamine, 2,3-dimethylindole gives 3-chloro-2,3-dimethylindolenine 2 which has chemical properties similar to 17 reacting readily with methanol to give 3. Similarly tetrahydrocarbazole was converted to the analogous chloroindolenine 5 and bromoindolenine 18 both of which readily underwent methanolysis to give 6 in good yield. A mechanism for the acid catalyzed methanolysis of 3-chloro- and 3-bromoindolenines is proposed.

Synthesis of Azocane- and Oxocane-Annulated Furans by a [2+2] Photocycloaddition–Ring-Opening Cascade

Synthesis ◽  
2020 ◽  
Author(s):  
Thorsten Bach ◽  
Xinyao Li ◽  
Christian Jandl
Keyword(s):  
Double Bond ◽  
Uv Irradiation ◽  
Alkyl Group ◽  
Ring Opening ◽  
Cascade Reaction ◽  
Coumarin Derivatives ◽  
Ring Opening Reaction ◽  
Acid Catalyzed ◽  
Subsequent Acid

AbstractThe title compounds were synthesized from readily available quinolone and coumarin derivatives by a cascade reaction (12 examples, 90–98% yield). The cascade comprised a [2+2] photocycloaddition which occurred upon sensitized irradiation at λ = 420 nm (or direct UV irradiation at λ = 366 nm) and a subsequent acid-catalyzed ring-opening reaction. A variety of substituents are compatible with the conditions and a 3-alkyl group in the coumarin (or quinolone) is crucial to achieve a high chemoselectivity. Key to the success of the ring opening is the formation of a 4,5,5a-trihydrocyclobuta-2H-furan containing a strained bridgehead double bond which stems from the allenyl group tethered to the 4-position of the starting materials.

Regio- and Stereoselective Synthesis of a Novel Family of Unsaturated Compounds with the S–Se Bond and Their Cyclization to 2,3-Dihydro-1,4-thiaselenines

Synthesis ◽  
2019 ◽  
Vol 51 (08) ◽  
pp. 1832-1840 ◽  
Author(s):  
Svetlana Amosova ◽  
Andrey Filippov ◽  
Vladimir Potapov ◽  
Maxim Penzik ◽  
Nataliya Makhaeva ◽  
...  
Keyword(s):  
Ring Opening ◽  
Room Temperature ◽  
Stereoselective Synthesis ◽  
Reaction Times ◽  
Nucleophilic Attack ◽  
Selenium Atom ◽  
Efficient Synthesis ◽  
Reaction Conditions ◽  
Ring Opening Reaction ◽  
Acid Catalyzed

Regio- and stereoselective ring-opening reaction of 2-bromomethyl-1,3-thiaselenole with thiols proceeded as nucleophilic attack at the selenium atom of seleniranium intermediate affording unsaturated selanyl sulfides, (Z)-CH2=CHSCH=CHSeSR, in up to 93% yield. Dithiols were involved in this reaction giving symmetrical polyunsaturated compounds with two S–Se bonds in 70–75% yields. Efficient synthesis of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines in 69–96% yields was developed by the acid-catalyzed cyclization of the unsaturated selanyl sulfides. Mild reaction conditions (room temperature) and short reaction times are important features of this methodology.

THE INFLUENCE OF SUBSTITUENTS ON THE EASE AND DIRECTION OF RING OPENING IN THE LiAlH4–AlCl3 REDUCTIVE CLEAVAGE OF SUBSTITUTED 1,3-DIOXOLANES

1964 ◽  
Vol 42 (5) ◽  
pp. 990-1004 ◽  
Author(s):  
B. E. Leggetter ◽  
R. K. Brown
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Ring Opening ◽  
Room Temperature ◽  
Reductive Cleavage ◽  
The Other ◽  
Ring Cleavage ◽  
Other Hand ◽  
Influence Of Substituents

The room temperature hydrogenolysis by LiAlH4–AlCl3 of ether solutions of a number of 1,3-dioxolanes has been studied.Electron donor substituents on the C2 atom of the ring accelerate while electron acceptor substituents on C2 retard the reductive ring cleavage. The same effect but to a lesser extent is observed when these substituents are attached to the C4 or C5 atom of the ring.When electron donor substituents are attached to C4, ring cleavage occurs predominantly at the C2—O bond remote from the C4 position. On the other hand, electron-withdrawing groups attached to C4 give predominantly scission of the C2—O bond closer to the C4-substituted position. In contrast to this marked control over the direction of ring cleavage exhibited by substituents on C4, those on C2 generally have little or no effect on the direction of ring opening.A mechanistic interpretation of the results is presented.

Cycloadditionen von Ketenen mit Fulvenen/Cycloadditions of Ketenes with Fulvenes

1983 ◽  
Vol 38 (4) ◽  
pp. 504-515 ◽  
Author(s):  
Willy Friedrichsena ◽  
Tony Debaerdemaeker ◽  
Andreas Böttcher ◽  
Sabine Hahnemann ◽  
Regine Schmidt
Keyword(s):  
Ring Opening ◽  
Sodium Methoxide ◽  
Ring Cleavage ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ring Opening Reaction ◽  
Acid Catalyzed

Fulvenes (1) add ketenes (2) in a [ π 2 + π 2] manner to give bicyclo[3.2.0]heptenes (3). Ring cleavage with sodium methoxide yields dihydrofulvenes (4) which can be deliydrogenated to give fulvenes (5), whereas the acid catalyzed ring opening reaction of 3 leads to fulvenes (6). The structure of 3h has been clarified by X-ray crystallography.

Two-Step Synthesis of α,β-Unsaturated γ-Amino Acid Esters via N-Heterocyclic Carbene Catalyzed [4+2] Cycloaddition of Enals and Nitroso Compounds

Synthesis ◽  
2017 ◽  
Vol 50 (01) ◽  
pp. 127-133
Author(s):  
Dieter Enders ◽  
Qiang Liu ◽  
Xiang-Yu Chen ◽  
Sun Li ◽  
Fabrizio Vetica ◽  
...  
Keyword(s):  
Amino Acid ◽  
Ring Opening ◽  
Nitroso Compounds ◽  
Amino Acid Esters ◽  
Efficient Strategy ◽  
Acid Catalyzed ◽  
Aromatic Nitroso Compounds ◽  
Subsequent Acid ◽  
Acid Esters

An efficient strategy for the synthesis of various of α,β-unsaturated γ-amino acid esters has been established employing N-heterocyclic carbene catalyzed [4+2] cycloadditions of β-methyl enals and aromatic nitroso compounds to afford 1,2-oxazin-6-ones in good yields. A subsequent acid-catalyzed esterification under ring opening yields the γ-amino enoates in good yields.

Tri(tert-butyl)methylenphosphoran : Konsequenzen sterischer Hinderung für innermolekulare Beweglichkeit und thermischen Zerfallsmechanismus / Tri(tert-butyl)methylenephosphorane : Consequences of Sterical Hindrance for Intramolecular Motions and Thermal Decomposition Mechanism

1977 ◽  
Vol 32 (7) ◽  
pp. 757-761 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Günter Blaschke ◽  
Frank H. Köhler
Keyword(s):  
Room Temperature ◽  
Hydrogen Exchange ◽  
Thermal Decomposition Mechanism ◽  
Tert Butyl ◽  
Bond Rotation ◽  
Mild Conditions ◽  
Steric Crowding ◽  
Sterical Hindrance ◽  
Intramolecular Motions ◽  
C Nmr

Dimethyl(tert-butyl)-, di(tert-butyl)methyl- and tri(tert-butyl)methylenephosphorane (CH3)n[(CH3)3C]3-nP=CH2, 3a-c, (n = 2,1, 0) have been synthesized from the corresponding phosphonium bromides, using standard methods, but under mild conditions. 3 c was found to be thermally unstable, undergoing reductive elimination of isobutene already at room temperature, with di(tert-butyl)methylphosphine as a by-product. 3 b is decomposed similarly above 80 °C. A mechanism for this unusual mode of ylide decomposition is proposed, based on the extreme steric crowding of the molecules. Restricted P–C bond rotation has been detected by 1H and 13C NMR spectroscopy for 3 c in toluene solution. Traces of protic species cause a rapid intermolecular H2C(P) hydrogen exchange.

The epoxidation of canola oil and its derivatives

RSC Advances ◽  
2016 ◽  
Vol 6 (95) ◽  
pp. 92874-92886 ◽  
Author(s):  
Tolibjon S. Omonov ◽  
Ereddad Kharraz ◽  
Jonathan M. Curtis
Keyword(s):  
Canola Oil ◽  
Ring Opening ◽  
Fatty Acid Methyl Esters ◽  
Methyl Esters ◽  
Epoxy Ring ◽  
Acid Methyl ◽  
Epoxy Ring Opening ◽  
Acid Catalyzed ◽  
Kinetics Of ◽  
Subsequent Acid

This work explores the epoxidation and subsequent acid catalyzed epoxy ring opening kinetics of canola oil (CanO), canola oil fatty acid methyl esters (CanFAME) and canola oil free fatty acids (CanFFA).

Beiträge zur Chemie des Phosphors, 242 Tri-tert-butylcyclotriphosphan-monoxid, (PBut )3O - Bildung und 31P-NMR-spektroskopische Strukturbestimmung/ Contributions to the Chemistry of Phosphorus, 242 Tri-tert-butylcyclotriphosphane Monoxide, (PButO — Formation and Structure Determination by 31P NMR Spectroscopy

1999 ◽  
Vol 54 (11) ◽  
pp. 1457-1462 ◽  
Author(s):  
Marianne Baudler ◽  
Christoph Breitkopf
Keyword(s):  
Nmr Spectroscopy ◽  
Structure Determination ◽  
Room Temperature ◽  
31P Nmr ◽  
31P Nmr Spectroscopy ◽  
Open Chain ◽  
Tert Butyl ◽  
Nmr Parameters

The partially oxidized cyclotriphosphane (PB ut)3O (1,2,3-tri-tert-butyl-1-oxocyclotriphosphane) (1) has been obtained by [2 + 1] cyclocondensation of K (But)P-P(But)K with ButP(O)Cl2 in toluene at -78 °C. The cyclophosphanes (PBut)4 and (PBut)3 as well as small amounts of the open-chain triphosphane [ButP(O)Cl]2P (O)But are also formed. In contrast to the unoxidized compound (PBut)3, compound 1 is not stable at room temperature, but decomposes above -30 °C undergoing rearrangement into the cyclotetraphosphanes (PBut)4 O (2), (PBut)4O2 (3), and (PBut)4. The 31P NMR parameters of 1 and 3 are reported and discussed.

Sign in / Sign up

Export Citation Format

Share Document