Bicyclo hexanes structure

Nonconjugated dienes and polyenes have triplet photochemistry which may be considered to arise from intramolecular interaction of one excited double bond with an isolated ground-state double bond. For example, the photocyclization of enrfo-dicyclopentadiene can be effected using acetone as a sensitizer.286 Other more flexible 1,5-dienes, when sensitized to triplet states, cross couple to yield bicyclo[2.1.1]-hexane structures. For instance, triplet mercury atoms convert both 1,5-hexadiene and 1,5-cyclooctadiene to such structures.267 Irradiation of the cyclooctadiene in the presence of cuprous chloride produces the tricyclo derivative in good yield266 but recent evidence again indicates that this latter reaction may proceed via free-radical intermediates.269... 

Summary The reactivity of some trichlorosilane-derived silazanes has been studied. Treatment of 2-amino-l,3-bis(trimethylsilyl)-l,3-diaza-2-silacyclopentane (2) with two equivalents of n-butyllithium results in the formation of its hexameric W,A-dilithium derivative 3, the structure skeleton of which is best described as a singly truncated but lithium-centered rhombic dodecahedron of eight lithium and five nitrogen atoms. Reduction of Si-Cl-containing silazanes with lithium alanate opens a straightforward access to aminoalanes. Bis[(tert-butylamino)chloroalane] (8), bis[(tert-butyl-amino)alane] (9), and l,3-di-/er/-butyl-lC7 , 3CT -diaza-2o , 60 -dialumina[2.1.1]bicyclo-hexane (10) have been synthesized and structurally characterized. 

Theoretical calculation at the HF/6-31G level99,102 on some S-S dications and their precursors have shown that the electronic structure of 1,4-dithionia-bicyclo[2.2.0]hexane and the sp-sp conformation of the tetramethyldisulfonium dication, the difference in the energy levels of [S] — [S] and [S] + n[S]103 is decreased owing to steric strain and the order of orbitals thus corresponds to case B. In the less strained systems (l,5-dithioniabicyclo[3.3.0]octane, 1,4-dithioniabicyclo[3.2.0]heptane), the order of orbitals corresponds to case C. Interestingly, ap-ap conformer of tetramethyldisulfonium dication was reported to correspond to case A. 

The structures of [2]ladderane and [3]ladderane were determined by electron diffraction.22,23 Each cyclobutane ring of bicyclo[2.2.0]hexane has a folded structure with fold angle 11.5°, and the molecule has C2 symmetry.22 Anti- and yy/7-tricyclo[4.2.0.02,5]octanes also have folded cyclobutane rings with fold angles of 8.0 and 9.0°, respectively.23 MM2 calculations on... 

Oxaspiropentanes have been generated and rearranged in a large variety of different environments. A series of alkylidene- and allylidenecyclopropanes, present in the structures of bicy-clo[3.1.0]hexanes or bicyclo[4.1.0]heptanes, were epoxidized and rearranged in situ to bicyclic ketones with the alkyl or allyl group preferentially to exclusively in the exo position (Table 4).51 This corresponds to a preferential to exclusive epoxidation of the corresponding alkenes from the sterically less demanding exo face. 

Therefore, on the basis of their carbon skeletons, the bicyclic terpenes belong to the following condensed ring structures tbujane type to bicycloQ3.1.0 ]hexane carane type to bicyclo Q4.1.0 ]heptane pinane type to bicyclo Q3.1.1I]heptane and... 

Since thujane contains as ring substituents an isopropyl group as well as a methyl group, the name "northujane (see Appendix D) does not conform to the terpene traditional definition of nor. The bicyclo plan name, that is bicyclo[23.1.0 ]hexane, is therefore recommended for the name of the parent ring structure of thujane, the fourth fundamental type of bicyclic terpenes. 

Bicyclic Thu jane Group Bicyclo[3.1.0]hexane Type 10, p.44 Based on Parent Structure Larger Than Ring Fixed Numbering Based on Ring Carbon Structure B icydo Numbering... 

Rule 6 Form the names of radicals derived from bicyclo[3.1.0]hexane names regularly according to established practices for naming radicals derived from bicyclic structures. Examples bicyclo[3.1.0]hex-2-yl, bicyclo[3.1.0]hex-3-en-2-yl, -isopropylbicyclo[3.1.0]hex-2-en-2-yl. 

TABLE 20. Structures of group 14 analogs of bicyclo[1.1.0]butanes, of their cation radicals and of metallabicyclo[2.2.0]hexanes (pm, deg)... 

A situation similar to that of the pair 141 and 143 with respect to octant or antioctant behavior, respectively, can be expected for the (structurally rigid) (2R)-bicyclo[3.1.0]hexan-2-one (147) and (2S)-6,6-dimethylbicyclo[3.1.0]hexan-2-one (148). Contrary to the pair 141 and 143, however, both compounds 147 and 148 show antioctant behavior with positive (n, tc ) Cotton effects (Afi298 + 1 83 (147) Ae307 + 1.35... 

Corey and Streith found that the photolysis of pyrone and pyridone yields bicyclo[2.2.0]hexane analogs 133). They suggested that the product has a structure formed by formal addition of carbon dioxide to cyclobutadiene (126). 

Cyclopropyl-substituted 1,3-dienes react in the normal fashion in the Diels-Alder reaction. Most of the dienes have been incorporated in cyclic structures with additional strain added to the cyclopropane ring. Compounds of this type that have been studied rather extensively, include derivatives of 3,4-dimethylenetricyclo[3.1.0.0 "]hexane, " bicyclo[4.1.0]hexa-2,4-diene, ""- - """ spiro[2.4]hepta-4,6-diene, - -" - "-" - " - ° - " -... 

Various bi- and polycyclic hydrocarbons containing bicyclo[3.1.0]hexane, spiro[2.4]heptane, or other structural units encompassing a three-membered ring, can produce six-membered ring compounds on thermal decomposition. Most thermolyses of this type have been carried out in the gas phase at low pressures, and kinetic parameters have been measured for many of these decompositions. Yields of the major products, even when not specifically noted, were usually high, but additional minor products were frequently detected (Table 1). Most thermochemical rearrangements of cyclopropane containing hydrocarbons proceeded via diradical intermediates, but concerted mechanisms were invoked in a few instances such as that of anti-tricyclo[3.1.0.0 " ]hexane. 

The trishomocyclopropenium ion (CeH/, 199) was first proposed by Winstein and coworkers as an intermediate in the solvolysis of czs-bicyclo[3.1.0] hexyl tosylate and extensive efforts were directed toward its generation under stable ion conditions. The persistent cation 199 was first prepared by Masamune et al. by the ionization of czx-bicyclo[3.1.0]hexane in superacid media and it has since been generated from the corresponding alcohol [Eq. (5.29)]. The NMR spectra of structure 199 are consistent with an ion of Csv symmetry. The three equivalent C-H groups are found at high field in the C NMR spectrum (8 C 4.9,7c h = 195.4Hz) in accordance with their hypercoordinate environments. 

Fig. 11.6 Structures of bridged bicyclic proline mimetics (22) 2-aza-bicyclo[2.2.1]hep-tane-3-carboxylic acid, (23) 2-aza-bicy-clo[2.2.1]hept-5-ene-3-carboxylic acid, (24) 7-aza-bicyclo[2.2.1]heptane-l-carboxylic acid, (25) 2-aza-bicyclo[2.2.1]hexane-l carboxylic acid, (26) 2-aza-bicyclo[2.2.1]hexane-...

Problem 9.1 Draw structural formulas for (a) bromocycloheptane, (ft) 1-ethylcyclopentene, (c) bicyclo-[3.1.0]hexane, (d) cyclobutylcyclohexane. 

In combination with the order matrix calculation, RDCs have been used to unambiguously solve the complete relative stereochemistry of substituted bicyclo[3.1.0]hexane with five stereocentres whose structure is shown in Fig. 8. The RDCs measured were C-C, C-F, H-F and H-H, and the complete relative stereochemistry of the compound has been solved by their use only. 

In Table 6, which was compiled from work on bicyclo[n.l.O]alkanes, bicyclo[1.1.0]-butanes, bicyclo[2.1.0]hexanes, bicyclo[2.2.1]heptanes , bicyclo[3.1.1]heptanes bicyclo[2.2.2]octanes ", bicyclo[3.3.0]octanes", bicyclo[4.n.0]alkanes, bicyclo[3.3.13-nonanes" spiro[4.5]alkanes" and trans-decalins the chemical shifts of several bicyclic alkanes are tabulated. The values were mainly explained by the steric effects present in the different structural environments, with the exception of fused cyclopropane rings (see below). 

The gas-phase reactions of HeT with bicyclo[2.1.0]pentane, bicyclo[3.1.0]hexane and bicyclo[4.1.0]heptane (41) have been investigated and the formation of tritiated hydrocarbons retaining the bicyclic structure of the starting substrate has been observed. This finding indicates that the gaseous bicycloalkylium ions are formed via exothermic trition transfer from the HeT to the bicyclic substrate (equation 107). Due to the... 

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