Chemistry of the Podocarpaceae. XX. Epoxides of ring-A-unsaturated 12-Methoxypodocarpa-8,11,13-trienes

1969 ◽  
Vol 22 (8) ◽  
pp. 1699 ◽  
Author(s):  
RC Canbie ◽  
WA Denny
Keyword(s):  
Boron Trifluoride ◽  
High Yield ◽  
Epoxide Ring ◽  
Oxidative Decarboxylation ◽  
Derivatives Of

Selective epoxidation of the methoxy alkene mixture (IX) from oxidative decarboxylation of 12-methoxypodocarpa-8,11,13-trien-19-oic acid (I) provides a method of obtaining a high yield of the exocyclic alkene (VII) from the mixture. Isolation of the 3α,4α-epoxide (X) during the epoxidation allows the formation of C 3 oxygenated derivatives of 12- methoxypodocarpa-8,11,13-trien-19-oic acid. ��� Methods for opening the epoxide ring of (X) and of the 4α,5α- and 4α,19-epoxides, (XI) and (XII), have been examined, and the structures of the products from rearrangement of each epoxide with boron trifluoride have been assigned.

Aminocyclitols. II. Synthesis of thioanalogues of 2,5-dideoxystreptamine

1978 ◽  
Vol 56 (21) ◽  
pp. 2743-2749 ◽  
Author(s):  
Gerry Kavadias ◽  
Robert Droghini
Keyword(s):  
Thionyl Chloride ◽  
Boron Trifluoride ◽  
Protective Groups ◽  
Thiobenzoic Acid ◽  
Derivatives Of ◽  
L 13

N,N′-Dibenzoyl-2,5-dideoxystreptamine (8b) reacted with thionyl chloride to form the bisoxazoline 9 and the latter compound was treated with thiobenzoic acid to produce the dithiobenzoate 10a. Removal of the protective groups in 10a afforded (l,3/4,6)-4,6-diamino-1,3-cyclohexanedithiol (1) dihydrochloride. Reaction of 8b with triethyl orthoacetate in the presence of boron trifluoride yielded the monooxazoline 12 which, on reaction with thiobenzoic acid followed by deprotection of the resulting 13a, afforded (d,l)-(13/4,6)-4,6-diamino-3-hydroxycyclohexanethiol (2) dihydrochloride. Similarly, 3-N-benzoyl-1-N-ethoxycarbonyl-2,5-dideoxystreptamine (15) and l-N-benzoyl-3-N-ethoxycarbonyl-2,5-dideoxystreptamine (20) were converted via their respective oxazolines 17a and 22a, to the enantiomeric aminothiols 3 and 4. Protected derivatives of 1–4 are also described.

scholarly journals Allyl type monomers for hard surface coating protection

2019 ◽  
Vol 140 ◽  
pp. 02007
Author(s):  
Larisa Popova ◽  
Anzhelika Tsyrulnikova ◽  
Sergey Vershilov ◽  
Julia Bazarnova ◽  
Ekaterina Aronova ◽  
...  
Keyword(s):  
Tetrabutylammonium Bromide ◽  
Environmental Safety ◽  
Carbon Chain ◽  
High Yield ◽  
Main Reaction ◽  
Fibrous Materials ◽  
Series Of Experiments ◽  
Work Up ◽  
Derivatives Of ◽  
Improve Mass Transfer

Based on the unsaturated derivatives of polyfluoroalkanols chemical products are used to protect solid and fibrous materials surface from the effects of water, oils and other pollutants. A method for obtaining allyl ethers of polyfluoroalkanols (polyfluoroalkoxypropenes) is based on the Williamson ether reaction. This method is a heterophase process. The use of solvents to improve mass transfer requires complementary measures to ensure industrial and environmental safety. It is more preferable to obtain the target ethers in water with PTC. A series of experiments using different chain length polyfluoroalkanols was studied by GLC. Kovats retention indexes of the target ethers were determined. It was found that in the case of lower homologues (CF3CH2OH, (CF3)2CHOH, HCF2CF2CH2OH), the addition of 5-15 vol.% 1,4-dioxane as a solubilizer provides a high yield of products. The application of PTC (tetrabutylammonium bromide) is indispensable for using polyfluoroalkanols with a longer carbon chain (C≥5). PTC invariably provides the almost complete conversion of polyfluoroalkanols. The decomposition process of TBAB becomes noticeable (GLC method) upon completion of the main reaction. Polyfluoroalkoxypropenes form azeotrope with water, which can be used in the work up process.

scholarly journals Formation and Thermal Behaviors of Ternary Silicon Oxycarbides derived from Silsesquioxane Derivatives

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1721
Author(s):  
Yoshiaki Iwase ◽  
Teruaki Fuchigami ◽  
Yoji Horie ◽  
Yusuke Daiko ◽  
Sawao Honda ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
Sol Gel ◽  
Silicon Oxycarbide ◽  
High Yield ◽  
Amorphous Sio2 ◽  
Gaseous Hydrocarbon ◽  
Spectroscopic Analyses ◽  
Sio2 Nanocomposites ◽  
Derivatives Of

Silsesquioxane (SQ) derivatives possessing intramolecular H2C = CH- groups and Si-H groups were designed as precursors for ternary silicon oxycarbide (SiOC). By using R-Si(OMe)3, H-Si(OEt)3 and (H-Si(Me)2)2O as starting compounds, SQ derivatives of VH-SQ (R = vinyl) and St-H-SQ (R = stylyl) were successfully synthesized through the conventional sol-gel route. Simultaneous thermogravimetric and mass spectroscopic analyses up to 1000 °C revealed that in situ cross-linking via hydrosilylation and demethanation of VH-SQ suppressed the evolution of gaseous hydrocarbon species to afford amorphous SiOC having a composition close to the desired stoichiometric SiO2(1−x)Cx (x = ca. 0.3) with a high yield. The effect of carbon content on the phase separation and crystallization of the SQ-derived amorphous SiOC was studied by several spectroscopic analyses and TEM observation. The results were discussed aiming to develop a novel polymer-derived ceramics (PDCs) route for in situ formation of binary β-SiC-amorphous SiO2 nanocomposites with enhanced thermal and mechanical stability.

4,5-Seco-4,6-cyclosteroids. III. Observations on the course of reductive rearrangement of 6β-Bromo-4β,5-epoxy-5β-cholestan-3β-ol

1969 ◽  
Vol 22 (4) ◽  
pp. 807 ◽  
Author(s):  
DJ Collins ◽  
JJ Hobbs ◽  
RJ Rawson
Keyword(s):  
Hydrogen Bromide ◽  
High Yield ◽  
Lithium Aluminium Hydride ◽  
Experimental Conditions ◽  
Lithium Aluminium ◽  
Reaction Proceeds ◽  
Derivatives Of

It has been shown that reductive rearrangement of 6β-bromo-4β,5-epoxy- 5β-cholestan-3β-ol (I) to 4,5-seco-4,6-cycle-6β-cholestane-3β,5α-diol (IXa) with lithium aluminium hydride in tetrahydrofuran proceeds via 6β-bromo-5β-cholestane-3β,5-diol (IIa). Relevant reactions of the latter and the corresponding 3-ketone are discussed. ��� Similar conversion of the 3-epimer of (I) into 4,5-seco-4,6-cyclo- 6β-cholestane-3α,5α-diol (XIIIa) in high yield indicates that reductive rearrangement of the 6β-bromo-5β-hydroxy moiety proceeds without participation of the 3-aluminate complex. Some derivatives of (XIIIa) are described. ��� Experimental conditions required for the conversion of (I) into (IXa) are defined. ��� Combined evidence indicates that the reaction proceeds in a concerted manner by essentially base-catalysed, 1,3-elimination of hydrogen bromide from diol (IIa) with 4,5-bond migration to give the formal intermediate 3β-hydroxy-4,5-seco-4,6-cyclo-6β-cholestan-5-one (VI), further reduced to (IXa).

General Method of Preparation of N-[(S)-(3-Hydroxy-2-phosphonomethoxypropyl)] Derivatives of Heterocyclic Bases

1993 ◽  
Vol 58 (5) ◽  
pp. 1151-1163 ◽  
Author(s):  
Petr Alexander ◽  
Antonín Holý
Keyword(s):  
Sodium Salt ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Cesium Carbonate ◽  
Analogous Reaction ◽  
Sodium Salts ◽  
Heterocyclic Bases ◽  
Derivatives Of ◽  
General Method ◽  
Methanolic Ammonia

Reaction of (R)-1-O-p-toluenesulfonyl-1,2,3-propanetriol (IV) with N-trimethylacetylimidazole (II) afforded (R)-1-O-p-toluenesulfonyl-3-O-trimethyacetyl-1,2,3-propanetriol (V) which was reacted with dimethoxymethane in the presence of phosphorus pentoxide to give (R)-2-O-methoxymethyl-1-O-p-toluenesulfonyl-3-O-trimethyacetyl-1,2,3-propanetriol (VI). Compound VI was treated with acetic anhydride and boron trifluoride etherate and the obtained 2-acetoxy derivative VII reacted with bromotrimethylsilane to give the intermediary bromomethyl ether VIII. Compound VIII on reaction with tris(2-propyl) phosphite afforded (R)-2-O-bis(2-propyl)phosphonomethyl-1-O-p-toluenesulfonyl-3-O-trimethyacetyl-1,2,3-propanetriol (IX). Condensation of synthon IX with sodium salts of adenine, 2,6-diaminopurine, or with cytosine, 6-azacytosine or 2-chloroadenine in the presence of cesium carbonate, afforded fully protected diesters X and XIIIb which on methanolysis and reaction with bromotrimethylsilane gave N-[(S)-(3-hydroxy-2-phosphonomethoxypropyl)] derivatives of adenine (XIa), 2- chloroadenine (XIb), 2,6-diaminopurine (XIc), cytosine (XIVa) and 6-azacytosine (XIVb). In an analogous reaction, sodium salt of 4-methoxy-2-pyrimidone reacted with compound IX to give an intermediate XIIIa which on treatment with methanolic ammonia and subsequent deblocking under the same conditions also afforded the cytosine derivative XIVa. Sodium salt of 2-amino-6-chloropurine was in this way converted into the corresponding 2-aminopurine derivative XVIII. Deprotection of this compound gave 9-(S)-(3-hydroxy-2-phosphonomethoxypropyl)-2-aminopurine (XIX).

Bromination of Tetralin. Short and Efficient Synthesis of 1,4-Dibromonaphthalene

2000 ◽  
Vol 65 (11) ◽  
pp. 1791-1804 ◽  
Author(s):  
Osman Çakmak ◽  
Ismail Kahveci ◽  
Íbrahim Demirtaş ◽  
Tuncer Hökelek ◽  
Keith Smith
Keyword(s):  
High Temperature ◽  
Major Product ◽  
High Yield ◽  
Efficient Synthesis ◽  
Secondary Products ◽  
Derivatives Of ◽  
Sole Product

High-temperature bromination of tetralin (1,2,3,4-tetrahydronaphthalene) with bromine resulted in benzylic bromination to give 1,4-dibromo-1,2,3,4-tetrahydronaphthalene (4) as a major product and several secondary products. Photolytic bromination of tetralin and subsequent double dehydrobromination of 1,1,4,4-tetrabromo-1,2,3,4-tetrahydronaphthalene (10) gave 1,4-dibromonaphthalene (11) as the sole product in a high yield. 1,4-Dibromonaphthalene is efficiently converted to the corresponding methoxy (12 and 13) and cyano (14 and 15) derivatives of naphthalene.

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