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Four-membered

The phosphoranes (4) and (5) have been obtained from the corresponding phosphines and diethyl peroxide. From the variable temperature n.m.r. spectrum of (5), below - 51 °C the phenyl group is locked in an equatorial position as in (5), between — 51 and 30 °C the pseudorotation (5) (6) is rapid on the n.m.r. time scale, and above 30 °C the pseudorotation (6) (7) is rapid. In the latter pseudorotation the strain involved in [Pg.31]

The diazaphosphetidinones (9 R = OMe or NMej) gave stable phos-phoranes (10) with benzil at - 70 °C, but the adduct of (9 R = NMcz) with diacetyl could not be isolated although there was n.m.r. evidence for its formation.  [Pg.32]

The bicyclic phosphite (11) with ozone gave a remarkably stable adduct (12) which decomposed to form singlet oxygen only above 0 °C. [Pg.32]


Under standard conditions of temperature and pressure (STP), the first four members of the alkane series (methane, ethane, propane, and butane) are gases. As length of the carbon increases the density of the compound increases (pentane) to C yHgg are liquids, and from C.,gH3g, the compounds exist as wax-like solids at STP. [Pg.90]

Nevertheless, there are situations where one wants to work with six four-membered rings in cubane (e.g., when considering the symmetry of the ring system). In this situation, one adds a sixth four-membered ring to obtain firom the SSSR the so-called extended set of smallest rings (ESSR). [Pg.56]

Th c values of V I, V2, and V3, in keal/tnol, are listed in mmp-tor.txtfdbf). fhc MM+ force field uses special values for the torsional force constants when the atoms are in a four-member ring. [Pg.187]

The most important disconnection for four-membered rings corresponds to the photochemical 2 + 2 cycloaddition of olefins ... [Pg.94]

Grandisol, with a four-membered ring, is another insect hormone, the male sex hormone of the boll weevil to be precise. It may also be useful as a highly specific pest control. How might it be made ... [Pg.136]

A few typical examples indicate the large variety of five-membered heterocycles, which can be synthesized efficiently by [2 + 3]-cycloadditions. [2 + 2]-Cycloadditions are useful in the synthesis of certain four-membered heterocycles (H. Ulrich, 1967), e.g. of 8-lactams (J.R. [Pg.152]

Examples of four-membered ring formation are rare. The cyclization of the cyclic allylic acetate 42 afforded a 2 1 mixture of the four-membered ring compound 43 and the six-membered ring compound 44[45]. [Pg.299]

The four-membered vinyloxetane 280 is cleaved with Pd(0j and used for allylation a homoallylic alcohol unit can be introduced into the keto ester 281 as a nucleophile with this reagent to form 282[168],... [Pg.328]

Intramolecular amination with allylic acetates is used for the synthesis of cyclic alkaloids 175]. Cyclization of 293 affords the six-membered ring compound 294 rather than a four-membered ring. The reaction is particularly... [Pg.329]

Later, fireflv oxyluciferin was successfully synthesi2ed (403. 408) and has been isolated and identified in firefly lanterns (luciola cruaciata) after the lanterns were treated with pyridine and acetic anhydride to prevent decomposition (409). In 1972, Suzuki and Goto firmly established that oxyluciferin is involved in the bioluminescence of firefly lanterns and in the chemiluminescence of firefly luciferin (403. 410).. A. mechanism involving a four-membered ring cyclic peroxide has been proposed for the reaction (406. 411). However, it was not confirmed by 0 -labelinE experiments (412). [Pg.421]

Lactones whose rings are three or four membered (a lactones and p lactones) are very reactive making their isolation difficult Special methods are normally required for the laboratory synthesis of small ring lactones as well as those that contain rings larger than SIX membered... [Pg.815]

Alkanes. The saturated open-chain (acyclic) hydrocarbons (C H2 +2) have names ending in -ane. The first four members have the trivial names methane (CH4), ethane (CH3CH3 or C2H5), propane (C3H8), and butane (C4Hjo). For the remainder of the alkanes, the first portion of the name... [Pg.1]

P-Hydroxy acids lose water, especially in the presence of an acid catalyst, to give a,P-unsaturated acids, and frequendy P,y-unsaturated acids. P-Hydroxy acids do not form lactones readily because of the difficulty of four-membered ring formation. The simplest P-lactone, P-propiolactone, can be made from ketene and formaldehyde in the presence of methyl borate but not from P-hydroxypropionic acid. P-Propiolactone [57-57-8] is a usehil intermediate for organic synthesis but caution should be exercised when handling this lactone because it is a known carcinogen. [Pg.517]

Fig. 1. Methods for representing SiO and AlO tetrahedra by means of (a) baH-and-stick model, (b) soHd tetrahedron, (c) skeletal tetrahedron, and (d) spare-filling of packed spheres (1). (e) Linking of four tetrahedra in a four-membered ring, (f) Secondary building unit called tmncated octahedron as... Fig. 1. Methods for representing SiO and AlO tetrahedra by means of (a) baH-and-stick model, (b) soHd tetrahedron, (c) skeletal tetrahedron, and (d) spare-filling of packed spheres (1). (e) Linking of four tetrahedra in a four-membered ring, (f) Secondary building unit called tmncated octahedron as...
The polymerizations of tetrahydrofuran [1693-74-9] (THF) and of oxetane [503-30-0] (OX) are classic examples of cationic ring-opening polymerizations. Under ideal conditions, the polymerization of the five-membered tetrahydrofuran ring is a reversible equiUbtium polymerization, whereas the polymerization of the strained four-membered oxetane ring is irreversible (1,2). [Pg.359]

The four-membered oxetane ring (trimethylene oxide [503-30-0]) has much higher ring strain, and irreversible ring-opening polymerization can occur rapidly to form polyoxetane [25722-06-9] ... [Pg.359]

Because of the high ring strain of the four-membered ring, even substituted oxetanes polymerize readily, ia contrast to substituted tetrahydrofurans, which have tittle tendency to undergo ring-opening homopolymerization (5). [Pg.359]


See other pages where Four-membered is mentioned: [Pg.21]    [Pg.2417]    [Pg.2779]    [Pg.55]    [Pg.56]    [Pg.326]    [Pg.147]    [Pg.117]    [Pg.129]    [Pg.130]    [Pg.131]    [Pg.132]    [Pg.133]    [Pg.134]    [Pg.94]    [Pg.35]    [Pg.315]    [Pg.140]    [Pg.396]    [Pg.113]    [Pg.732]    [Pg.147]    [Pg.150]    [Pg.293]    [Pg.191]    [Pg.449]    [Pg.445]    [Pg.452]    [Pg.494]    [Pg.369]    [Pg.484]   


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Annulated Three- and Four-Membered Heterocycles

Bidentate Ligands Forming Four-Membered Rings with Silicon

Carbenes Derived from Four-membered Heterocycles

Carbenes four-membered ring carbene

Carbocycles four-member

Cyclic boranes, four-membered

Cyclic boranes, four-membered bonding

Cycloaddition four-membered rings formation

Dioxetanes four-membered rings

FUSION TO FOUR-MEMBERED RINGS

Five-Membered Heterocycles with Four Hetero Atoms

Five-membered heterocycles with four heteroatom

Formation of a Four-Membered Ring

Formation of a Four-Membered Ring Oxetanes

Formation of four-membered rings

Forming four-membered

Forming four-membered heterocycles

Four membered rings, conformation

Four membered rings, formation using

Four- and Five-membered Ring Compounds

Four-Membered Heterocyles

Four-Membered Kings

Four-Membered Rings Photochemistry in Synthesis

Four-Membered Rings, frames

Four-Membered Unsaturated Rings

Four-membered Carbocyclic Systems

Four-membered Heterocycles containing a Single Nitrogen, Oxygen or Sulfur Atom

Four-membered NHC

Four-membered Rings as Neighbouring Groups

Four-membered Rings containing Oxygen and One Sulphur Atom

Four-membered Rings containing Sulphur and Oxygen

Four-membered Rings containing Sulphur and Silicon or Germanium

Four-membered Rings containing Sulphur, Nitrogen, and Phosphorus

Four-membered Rings with Y Group 15 atom

Four-membered and Larger Rings

Four-membered carbocycles

Four-membered carbocycles cycloaddition

Four-membered cycles

Four-membered cyclic amides

Four-membered heterocycle-derived

Four-membered heterocycle-derived carbenes

Four-membered heterocycles

Four-membered heterocycles aromaticity

Four-membered heterocycles photochemistry

Four-membered heterocycles with one

Four-membered heterocycles with two

Four-membered heterocycles, review

Four-membered heterocyclic compounds from

Four-membered heterocydes

Four-membered intermediate

Four-membered peroxides

Four-membered ring compounds

Four-membered ring compounds photochemical reactions

Four-membered ring compounds strain energy

Four-membered ring compounds synthesis

Four-membered ring formation

Four-membered ring heterocycles

Four-membered ring heterocycles azetidine-2-ones

Four-membered ring heterocycles azetidines

Four-membered ring systems

Four-membered ring systems 5-lactones

Four-membered ring systems monocyclic 2-azetidinones

Four-membered ring systems oxetanes

Four-membered ring systems silicon and phosphorus heterocycles

Four-membered rings

Four-membered rings 2- oxetanes

Four-membered rings 2-substituted oxetane-3-ones

Four-membered rings Chromium carbene complexes

Four-membered rings containing one sulfur

Four-membered rings containing one sulfur atom

Four-membered rings synthesis

Four-membered rings, heterocycle synthesis

Four-membered titanium oxide ring

Four-membered titanium oxide ring intermediate

Four-membered transition

Four-membered transition state

Fused Four-membered Carbocyclic Systems

Heterocyclic Four-Membered Rings, Stereochemistry of (Moriarty)

Heterocyclic compounds four-membered

Heterocyclic compounds four-membered ring opening

Heterocyclic compounds four-membered ring, formation

Heterocyclic compounds four-membered rings

Heterocyclic systems four-membered

Homologation of Four-Membered Heterocycles

Imine compounds four-membered rings

Ketones four-membered carbocycles

Lactones four-membered

Lithium-containing four-membered rings

Metallacycle four membered

Metallacycles four-membered

Miscellaneous Four-Membered Rings

Natural product synthesis four-membered ring formation

Nitrides four-membered rings

Nitrile imines four-membered rings

Of four-membered metallacycle

Other Four-membered Rings containing Sulphur and Nitrogen

Oxetane four-membered

Peri-Heterocycles with Four-Membered Heteroring

Phosphates, four-membered monomer

Phosphonium ylides four membered

Phosphorus heterocycles four-membered rings

Phosphorus heterocycles, four-membered

Photochemical four-membered ring synthesis

Photochemistry four-membered

Quinones with a Condensed Four-Membered Heterocyclic Ring

Reactions of Four-membered Rings

Reactions with Three- and Four-Membered Ring Systems

Ried, W„ Heinz, B„ Four-Membered Rings

Ried, W„ Heinz, B„ Four-Membered Rings Containing One Sulfur Atom

Ring Expansion from Four-membered Rings

Ring Expansion into Four-Membered Heterocycles

Ring compounds, structure four-membered

Silicon heterocycles, four-membered

Strained double four-membered

Subject four-membered rings

Sulfur compounds four-membered rings

Synthesis of Four-membered Rings

Systems Containing Four-membered Rings

Three, Four, and Five-membered Systems with One Heteroatom

Three- and Four-membered Ring Systems

Three- and four-membered rings

Three-, Four-, and Five-membered-ring Phosphoranes

Transformation of a Four-membered Ring

Transformation of four-membered rings

Transient Four-membered Rings

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