Bicyclo n.l.0 alkanes

The present procedure for ring expansion has also been applied to l,2-bis(trimethylsilyloxy)bicyclo[n.l.0]alkanes, which are prepared by cyclopropanation of l,2-bis(silyloxy)cycloalkenes. The latter are readily available from acyloin condensations in the presence of chlorotrimethylsilane. " This reaction provides a new route to cyclic 1,3-diketones and macrocyclic compounds containing two 1,3-diketone units in the ring. 

Intramolecular cyclopropanation with acceptor-substituted carbene complexes is a powerful method for the synthesis of bicyclo[n.l.0]alkanes [1359,1375-... 

Prior knowledge has shown the value of introducing cyclopropane systems into macromolecules. A number of isolated studies have been carried out on the polymerization of such structures (10, 14, 28), principally on cyclopropane (28) and isopropylcyclopropane. Attention was directed toward three types of structures—i.e., the 1,1-dichlorocyclopro-panes, the bicyclo[n.l.0]alkanes, and the spiro [2.n] alkanes. In each case, the effects involved appeared highly complex the polymers formed have not yet all been characterized, and it is thought that a comparison with the model structures expected from rupture of one or the other of the cyclopropane bonds may be of value. 

The solvolyses of several bicyclo[n.l.0]alkan-3-yl systems larger than [3.1.0] have been investigated for evidence of cyclopropyl participation. Although product studies have revealed interactions of the cyclopropanes in certain of these cases with the cationic center, it is not clear from the kinetic results whether the participation is also involved in the ratedetermining ionization or just in a subsequent step. 

Meldrum s acid is best introduced into a bicyclo[n.l. OJalkylamine system by its reaction with bicyclic A,0-acetals. Various amines such as morpholine, piperidine, pyrrolidine, dimethylamine, benzylamine, or azepane can be used for this reaction with c/j-bicyclic systems. Azepane as amino component is essential for the analogous reaction of a trans-bi-cyclo[9.1.0]dodecanone A,0-acetal. Both cw-bicyclo[n.l.0]alkane isomers 5 possessing Meldrum s acid either in the exo-position or in the enrfo-position were synthesized as sterically... 

Readily accessible l,2-bis(trimethylsiloxy)bicyclo[n.l.0]alkanes such as 5 were transformed to ring-expanded 1,3-diketones 6 under similar conditions. ... 

Medium and large rings can be made via cationic intermediates which are usually generated by treatment of suitable precursors with acid. Reactions of this class are perchloric acid catalyzed rearrangements of bicyclo[n.l.0]alkan-2-ols (n > 5), solvolysis of the corresponding esters, boron trifluoride-diethyl ether complex catalyzed cleavage of epoxides, and tri-fluoroacetic acid catalyzed reactions of 7-(methylsulfanyl)bicyclo[n.l.0]alkanes. 

Medium and large rings can be formed in thermal, photochemical, and other reactions of compounds containing the bicyclo[n.l. 0]alkane structural unit with n > 5. They are also formed in a variety of unique rearrangements, and in ring-expansion reactions proceeding via bi-cyclo[n. 1. OJalkan-1 -oxyl radicals. 

Scheme 11.38. Vinylcyclopropane to cyclopentene rearrangement in (n+3)-(dimethylamino)-l -ethenyl-bicyclo[n.l.0]alkanes 66...

A cyclic iminocarbene was transferred from 2-diazo-5-isopropyl-3,6-dimethoxy-2,5-dihy-dropyrazine to an alkene under unusually mild conditions. This diazo compound decomposes under the conditions of its synthesis from 2,5-dihydropyrazine 8, and in the presence of cy-cloalkenes, 2,5-dihydrospiro[pyrazine]bicyclo[n.l.0]alkanes 9 (n = 3-5) were obtained86 (an experimental procedure is given in Houben-Weyl Vol. E19b, pi 194). 

Dimethyl(succinimido)sulfonium fluorosulfate 2, easily prepared from /V-chlorosuccinimide (1), dimethyl sulfide, and methyl fluorosulfate, reacted with 1-dialkylaminocycloalkenes 3 to give fair yields of (2-dialkylaminocycloalk-l-enyl)dimethylsulfonium fluorosulfates 4 or their thermally rearranged allylic isomers 5.22 23 At elevated temperatures 4 or 5, respectively, reacted with nucleophiles Nu to give c -bicyclo[n.l.O]alkanes 8 or 9 via (Z,Z)-2-aminoallyl cation 6 or trans-bicyclo[n.l. 0]alkanes 12 via ( , Z)-2-aminoallyl cation 10, in fair to excellent yield.23 " 42 Normally, ra-annulated cyclopropylamines 8, resulting from kinetically preferred attack of... 

Polymerization of Bicyclo[n. 1.0]Alkanes. From the large-ring bicyclo[n.l.0]alkane series, six were chosen because of their relative ease of synthesis bicyclo[5.1.0]octane (M2), bicyclo[6.1.0]nonane (M3), bicyclo[ 10.1.0] tridecane (M4), and the corresponding 1-methylbicyclo-[n. 1.0] alkanes and prepared from the corresponding cycloalkenes or 1-methylcyclqalkenes (cycloheptene, cyclooctene, and cyclododecene). See Equation 4. 

Cationic Polymerization of BiCYCLo[n.l.0]ALKANES. The bicyclo [n.l.0]alkanes were polymerized in methylene chloride by various Lewis acids TiCl4, BF<-Et20, and SnCl4—with catalyst/monomer molar ratios from 4 to 15%. The temperatures used were between 20° and 80°C. At the lower temperatures and for the concentrations used, the degree... 

Bicyclo[n,l,0]alkan-2-ones are obtained in good yields on oxidation of bicyc-lo[n,l,0]alkanes with ozone adsorbed onto a silica gel. Bicyclo[n,l,0]alkan-3-ones and diketones are formed as side-products. ... 

The reaction of o>-halogeno-l-(NJV-dialkylamino)cycloalkenes with amines is known to result in a Favorskii-type ring contraction, giving rise to cm-diamino-bicyclo[n,l,0]alkanes, but, under the same conditions, the acyclic analogue (28) yields predominantly acyclic products. However, by employing (28), AgBF, and MejNH in a molar ratio of 1 1 2, cyclization is almost quantitative. Starting from... 

The stereoselective rearrangement of medium-ring bicyclo[n,l,0]alkan-2-ols has been observed for the first time in a large-ring counterpart. Thus treatment of the trans, anti-alcohol (66) with acid affords the trans-cycloalkenol (167) in a highly... 

Thermal Reactions.— Vinylcyclopropanes and Related Compounds. The trimethyl-silyl enol ether-vinylcyclopropane rearrangement has been extended to bicyclo-[n,l,0]alkane systems (n = 3—5). With the silyl enol ether at the 1-position... 

As a result, a living /controlled free-radical polymerization via an atom transfer radical polymerization (ATRP) mechanism has been described for methyl 1-bicyclobutane carboxylate, providing decently narrow molecular weight distributions and adequate control of the molecular weights [4, 75]. An A-B polystyrene diblock copolymer was also obtained by the same authors, using the bromo-terminatedpoly(bicyclobutanecarboxylate) as a macroinitiator. Bicyclo[n.l.0]alkanes with n> 1 have also been polymerized (Table 13.6). 

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