Bicyclo hexanes

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. 

Fig. 6. Synthesis of prostaglandins via a bicyclo[3.1.0]hexane intermediate where MCPBA = m — chloroperbenzoic acid.

The 3-cyclohexeityl ion provides another example of the dependence of the extent of rearrangement on reaction conditions. The major product is the result of direct solvent displacement. There is also some product resulting from Itydride shift to the more stable allylic ion as well as a trace of the bicyclo[3.1.0]hexane product arising from participation of the double bond. ... 

Two different routes to PCs via bicyclo[3.1.0]hexane intermediates are shown. In route 1 stereo- and position-specific addition of dichloroketene to a bicyclo[3.1.0]hexene provided the framework for elaboration to prostanoids. Route 2 featured stereospecific internal cyclopropanation and stereospecific Sn2 displacement of carbon to establish the prostanoid nucleus. 

Photochemical cyclohex-2-enoneH> bicyclo (3.1.0) hexan-2-one rearrangement irradiation of testosterone acetate, 322 Photochemical rearrangements of cross-conjugated cyclohexadienones and their photoisomers... 

Photochemical cyclohex-2-enone bicyclo (3.1.0)hexan-2-one rearrangement, 320 Photochemical a-cyclopropyl ketone isomerization, 313... 

As described in Section 1.7.1, the utility of the Wenker reaction is limited to substrates without labile functionalities because of the involvement of strong acid and then strong base. The Fanta group prepared a variety of aziridines by taking advantage of the Wenker reaction.For example, 6-aza-bicyclo[3.1.0]hexane (14) was produced from the ring-closure of ( )-rra s-2-aminocyclopentanol hydrochloride (13). In a similar fashion, sulfate ester 16 was prepared from A-methyl dl-trans- >-ssmnoA-hydroxytetrahydrofuran (15). Subsequent treatment of sulfate ester 16 with NaOH then delivered aziridine I . " Additional examples of Wenker aziridine synthesis may also be found in references 15-17. 

An essentially quantitative yield (98%) of the thermally stable hexafluoro-2-aza-bicyclo[3.2.0]hepta-3,6-diene 18 is obtained from the small-scale photolysis of the hexafluoro-l//-azepine 17.230 Hexafluoro-l//-azepine-l-carbonitrileand-l-carboxamidebehave similarly. On scaling up the process for the l-(ethoxycarbonyl) derivative 17, however, a much lower yield (59%) of bicycle 18 resulted, although this was improved to 81% by carrying out the photolysis in hexane or rm-butyl alcohol in the presence of a triplet sensitizer, e. g. ben-zophenone. 

Hodgson very recently reported an efficient intramolecular and completely dia-stereoselective cyclopropanation of bisliomoallylic and trisliomoallylic epoxides based on the use of a-lithiated epoxides. In a seminal paper, Crandall and Lin had reported that the reaction between t-BuLi and l,2-epoxyhex-5-ene (100) gave, inter alia, small amounts oftrans-bicyclo[3.1.0]hexan-2-ol (102, 9%) (Eq. a, Scheme 8.28)... 

Adamantan2 In einem 100-m/-Kolben mit Magnetriihrer legt man unter Stickstoff 25 ml Pentan und 4,1m/ (20mMol) 9-Butyl-9-bora-bicyclo[3.3.1]nonan vor. BeiO° werden 20 mMol Butyl-lithium in Hexan ( 14,4m/) zugegcben. Dann riihrt man 1 Stde. bei 20°, tropft 4,3 g (20 mMol) 1 -Brom-adamantan bei 0° zu und riihrt 12—15 Stdn. bei 20°. Dann wird oxidicrt. Man trennt die organ. Phase ab und filtriert durch eine Saule mit 40 g Alumi-niumoxid. Man eluiert mit 60 ml Hexan und zicht das Losungsmittel ab Ausbeute 2,43 g (89% d.Th.) F 212-215° (Subl.). 

Chlor-l-brom-bicyclo[2.2.0]hexan wird an Quecksilber zu Bicyclo[2.2.0]hexen-(14) reduziert1 ... 

Gold catalysts containing NHC ligands can also promote cycloisomerisation reactions. Bicyclo[3.1.0]hexanes 137-139 can be prepared from the cycloisomerisation of 1,5-enynes bearing a propargyUc acetate (135) in the presence of catalytic amounts of [AuCl(lPr)]/AgBF (Scheme 5.36) [41]. The cycloisomerisation reaction of 135 occurs by a 1,3-OAc shift/aUene-ene cyclisation/l,2-OAc shift sequence. Experimental results with allenyl acetate 136 support this hypothesis as 139 is obtained in higher ratios than 137 and 138 [41b],... 

Data on the thermal isomerization of bicyclo [2,1,1] hexane were measured by Srinivasan and Levi (1963). The data are given in Table 4.4. The following nonlinear model was proposed to describe the fraction of original material remaining (y) as a function of time (x,) and temperature (x2). The model was reproduced from Draper and Smith (1998)... 

Table 16.4 Isomerization of Bicyclo [2,1,1] Hexane Reduction of the LS Objective Function...

Using the above parameter estimates the fraction of original material of bicyclo [2,1,1] hexane was calculated and is shown together with the data in Table 16.5. As seen the model matches the data well. 

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