Spiro-pentane

The very large value of the pre-exponential factor indicates a transition complex which is very loose compared with the highly strained spiro-pentane structure. Inspection of the models of the reactant and product makes it clear that considerable distortion of the reactant must occur on going to the transition complex. A minor reaction path results in the formation of allene and ethylene. These products are primary. 

In contrast, carbon vapor generated in a carbon arc deposits mixtures of thermally equilibrated C(1S), C(3D), and C(3P) atoms on the walls of the reaction vessel, where they can be reacted with olefins.16 The most energetic and shortest-lived species, CX S), apparently forms allenes and inserts into C—H bonds. The Q1/)) atoms yield spiro-pentanes by two stereospecific addition steps. After long periods only ground state C(3P) atoms remain, and they add to olefins partially stereospecifically as shown below to yield isomeric spiropentanes. 

CONTENTS Preface, Brian Halton. Matrix-Isolation of Strained Three-Membered Ring Systems, Wolfram Sander and Andreas Kirschfield. Synthetic Utility of Cyclobutanones, Harold W. Moore and Benjamin R. Xerxa. Electrophilic Additions to Bicyclo [1.1.0] butanes, Manfred Christl. From Spiro-pentanes to Linear and Angular Oligo- and Polytriangulanes, Armin de Meijere and Sergei Kozhushkov. [N] Staffanes, Piotr Kaszynski and Josef Michl. Index. ... 

Heats of formation of small hicyclic hydrocarbons, spiropentadiene (C5H4), spiro-pentane (CsHg) and hicyclo[1.1.0]hut-l(3)-ene (C4H4) a theoretical study by the... 

Thermolysis of Spiro-compounds. It is already known that pyrolysis of spiro-pentane gives products whose relative yields depend upon the pressure. Flowers and Gibbons have extended earlier work and shown that RRKM theory accounts for the pressure dependence of the reaction from lO Torr to 1 atm using either of two possible mechanisms. One mechanism involves intervention of a biradical intermediate, the other involves direct transformation of spiropentane into methylenecyclobutane, ethylene, and keten (and... 

E)-Spiro[12,ll]letracos-13-ene (2).3 Spiro tosylhydrazone 1 (0 275 g, 0 53 mmol) in diglyme (8 mL) under N2 was treated with MeONa (0 11 g. 2 mmol) Afterl h rellux the mixture was extracted with Et20. the extract washed (brine) and evaporated to afford 0 t6 g ol 2 (91%), mp 64 se C (pentane)... 

Table 1 summarizes the yields and selectivities of the addition of dienolate 2 to various aldehydes. It can be seen that the yield and enantioselectivity very much depend on the solvent, with THF being the best tested. The best results were obtained with pentanal (55% yield, 92% ee). On the other hand, when spiro dienolate 1 was used in these aldol reactions, benzaldehyde gave the best... 

Cyclic diazoalkanes have been used to generate spirocyclopropanes via ring contraction of pyrazolines formed in the initial cycloaddition step. Two novel examples are the transformation of 3-diazo-2-nitromethylenepiperidine (16) into 5-aza-spiro[2.5]octane 17 (45) and the conversion of 1-diazo-2-methylenecyclo-propane (18) into methylene-spiro[2.2]pentane 19 (46) (Scheme 8.6). Related reactions have also been reported for diazocyclopropane (47) and diazospiropen-tane (48). 

Catalytic hydrogenation is an obvious method for the conversion of cyclobutenes into cyclobutanes. Thus, hydrogenation of a solution of unstable spiro[3.4]octa-l,5,7-triene in pentane at — 40 °C over rhodium [prepared in situ from rhodium(III) chloride by reduction with sodium borohydride24] gave spiro[3.4]octane (9) as the major volatile product in over 90% yield.14... 

Protonation of spiro[2.2]pentane 482 yields the C5H9+ ions. Cation 483 was shown to be the initial protonated spiropentane by early experimental (MS) and theoretical... 

Furthermore, Wessig and Muhling were successful in synthesizing highly strained spiro[2.2]pentanes in l,l,2-trichloro-l,2,2-trifluoroethane (R113) (Scheme 4.51) [74],... 

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