Ring compounds bridged substitution

Lactam formation from an oxidative cleavage of the bicyclic zero bridge is well known, for example, VIII/197 — VIII/200 [115]. Because of the relative positions of a ketone and a secondary lactam in the ten-membered ring compound, VIII/199, however the only stable structure is that of the fused five/seven ring system in VIII/200 [116]. The substituted 3(2H)-pyrazolones VIII/201 are opened oxidatively by periodate to VIII/202 [117]. 

Titanium complexes derived from ethylene-bridged 2-indenyl ligands (Scheme 650) have been prepared by reductive dehydroxy coupling of 2-(hydroxymethyl)indenes with low-valent titanium compounds. Alkyl substitution of the indene ring at C(3) improves the regioselectivity of the reductive coupling.1671... 

The Hantzsch-Widman system is well suited for the naming of saturated monocyclic compounds. Bridged ring systems, however, present a special challenge, and here the replacement system is preferred. An example is provided by the framework of the bicyclic hydrocarbon norbornane. Heteroatoms may in principle be substituted for any of the carbons. To illustrate, nitrogen substitution at position 7 would give rise to the name 7-azanorbomane. 

Another common polycyclic system is norbornane. Norbornane is the common name for bicyclo[2.2.1]heptane. We can think of this compound as a six-membered ring locked into a boat conformation by a CH2 group that serves as a bridge. Many naturally occurring compounds are substituted norbornanes, such as camphor and camphene ... 

Intramolecular reactions between donor and acceptor centres in fused ring systems provide a general route to bridged polycyclic systems. The cts-decalone mesylate given below contains two d -centres adjacent to the carbonyl function and one a -centre. Treatment of this compound with base leads to reversible enolate formation, and the C-3 carbanion substitutes the mesylate on C-7 (J. Gauthier, 1967 A. Belanger, 1968). 

Symmetrical diaLkyl peroxides are commonly named as such, eg, dimethyl peroxide. For unsymmetrical diaLkyl peroxides, the two radicals usually are hsted ia alphabetical order, eg, ethyl methyl peroxide. For organomineral peroxides or complex stmctures, ie, where R and R are difficult to name as radicals, the peroxide is named as an aLkyldioxy derivative, although alkylperoxy is stUl used by many authors. CycHc peroxides are normally named as heterocychc compounds, eg, 1,2-dioxane, or by substitutive oxa nomenclature, eg, 1,2-dioxacyclohexane however, when the two oxygens form a bridge between two carbon atoms of a ring, the terms epidioxy or epiperoxy are frequendy used. The resulting polycycHc stmcture has been called an endoperoxide, epiperoxide, or transaimular peroxide. 

The original acid—clay developers have been largely replaced by phenohc compounds, such as para-substituted phenohc novolaks. The alkyl group on the phenohc ring is typically butyl, octyl, nonyl, or phenyl. The acidity is higher than that of a typical unsubstituted novolak because of the high concentration of 2,2 -methylene bridges. 

Thermal stability is enhanced in chelates thus dimethyl-2-methy1pentane-2,4-dio1titanium [23916-35-0] (22) is much more stable than (CH2)3Ti(OCH(CH2)2)2 (68)- The stmcture of the former has been shown by x-ray diffraction to be dimeric and five-coordinate through oxygen bridges. The more highly substituted the six-membered ring, the mote thermally stable the compound. 

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