Olefination strained ring systems

In contrast to the strained ring systems discussed above, photolysis of the larger ring system in (7) results in olefin (8) as the major product(14> ... 

The next four procedures describe the preparation of strained ring systems. Preparation of 3-CHLORO-2-(CHLOROMETHYL)-l-PROPENE provides a facile approach to the olefin required for the synthesis of [1.1.1 [PROPELLANE, one of the most strained hydrocarbons prepared to date. The ready availability of this hydrocarbon should prove particularly useful to those interested in the development of the chemistry of this fascinating compound. Preparation of N-BENZYL-2,3-AZETIDINEDIONE provides an efficient approach to the unadorned a-keto-/3-lactam, a potential... 

The present preparation affords high-purity nortricyclanol in good yield without the necessity of tedious purification. It illustrates a convenient way to convert olefins to alcohols and to remove olefinic impurities from alcohols. Nortricyclanol is of current interest in studies of highly strained ring systems. It is readily oxidized to nortricyclanone. ... 

Opening of a strained ring system and the subsequent coupling with an acyclic alkene results in the formation of diene products. Because of many metathesis pathways available in the systems containing a cyclic and a linear olefin, the... 

Strained alkenes may have a combination of the strain in the basic ring system, and the added strain that results from the introduction of the double bond. Thus, it is convenient to define olefinic strain (OS) that may be given as the difference in heat of hydrogenation of the alkene in question and that of a similarly substituted... 

This obstacle can be overcome by moving electron withdrawing substituents away from the double bond and increasing the reactivity of double bond by positioning it in a strained ring. This is achieved using bicyclic monomers. The monomers are readily obtained from the Diels-Alder reactions of substituted olefins with cyclopentadiene. This route is effective also for fluorinated monomers. These types of monomers undergo a ROMP with a variety of one component and two-component initiator systems. 

Intramolecular cyclopropanation of diazoketones to furnish [3.1.0] and [4.1.0] bicyclic systems are the most common and effective reactions in this category. Two recent examples are shown in equations 48 and 49. The bicyclic ketone 34 has been used in the synthesis of polycyclic cyclobutane derivatives77, whereas ketone 35 is the key intermediate in the total synthesis of ( )-cyclolaurene78. When the olefinic double bond is attached to, or is part of, a ring system, the cyclopropanation process also works well. Copper oxide catalysed decomposition of diazoketone 36 produces the strained tricyclic ketone 37 in 86% yield (equation 50)79. In another case, in which the cyclopropanation of diazoketone 38 gave stereospecifically the cyclopropyl ketone 39, copper sulphate catalysis was used. The cyclopropyl ketone 39 is the key intermediate in the total synthesis of ( )-albene 40 (equation 51). ... 

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