Bicydes reactions

Treatment of a stannylenyne/enene compound with a low-valent zirconocene derivative results in a bicydization reaction leading to the 1,1-stanniozirconocene complex 99 (Scheme 7.29) in moderate yield [168], The product of carbonylation of 99 can be readily... 

The most widely applicable method for the synthesis of 1-substituted J//-l,2-diazepines 8 is photoisomerization of pyridinium 1-imides 6. The reaction is presumed to proceed by way of the bicydic intermediates 7, which, however, have not been detected (see Houben-Weyl, Vol. 4/ 5a, p584ff) selected examples are given.75-77... 

The aza-[2,3]-Wittig rearrangement of a vinylaziridine-derived quaternary azir-idinium ylide (i.e., [2,3]-Stevens rearrangement) has recently been reported (Scheme 2.53) [86], The aziridinium ylide 219, generated by the intramolecular reaction of a copper carbenoid tethered to a vinylaziridine, underwent a [2,3]-Ste-vens rearrangement to furnish the bicydic amine 220 with the indolizidine skeleton. 

An elimination/double Wagner-Meerwein rearrangement process has recently been developed by Langer and coworkers [39]. Treatment of compound 1-136, obtained by reaction of 1-134 and 1-135, with trifluoroacetic acid (TFA) led to the cationic species 1-137, which then underwent a twofold Wagner-Meerwein rearrangement to give the bicydic compound 1-139 via 1-138 (Scheme 1.34). 

Oxidation of alkenes and dienes involving an allene substituent as a formal nucleophile is a conceptually new reaction. Allcnc-substitutcd 1,3-cyclohexadienes 34 undergo a pal-ladium(II)-catalyzed oxidation to give bicydic compounds 35 or 36 in good yields (Scheme 17.14) [14]. When y-alkenylallenes, e.g. 37, 41 and 43, were treated with 1 mol% palladium trifluoroacetate, a similar oxidative carbocyclization took place [15]. In both reactions the new stereocenters are formed with high stereoselectivity. 

Rhodium(ll)-catalyzed transformation of diazo-pentadione derivatives 273 into the ylide 274 and subsequent cycloaddition to affords bicydic adducts 275 in goodyields (30-50%) (Scheme 4.48) [317,318].The reaction doesnotrequire heating and can be performed with various R groups, e.g. ferrocene, aryl-, alkyl- or thiophene substituents. 

Alternatively, fluorinated aminoesters with the enyne structure were transformed into a variety of vinyl cyclic amino acid derivatives and related bicydic derivatives via Diels-Alder and oxidation reactions [38] (Sdieme 8.6). 

Bicydic products were obtained from C—C-reductive elimination of a presumed rhodacyde intermediate (see 33). Both of Uemura s reactions constitute significant contributions to the catalysis literature because they involve (i) vinylidenes, (ii) catalysis of a pericyclic process, and (iii) C—H bond activation. 

During the studies of Lee et al. with several organometallic reagents for the development of new [5-lactam antibiotics a gold-catalyzed synthesis of bicydic 15-lactams 28 was described. In this case, the suggested reaction pathway also involved a vinyl gold intermediate [41]. 

Photoadditions that arise by initial excitation of the aromatic compound are not common. Benzvalenes are readily attacked by hydroxylic compounds, and so irradiation of benzene in aqueous solutions of acetic acid, for example, results in the formation of a bicydic product (and an isomer derived from it by subsequent photoisomerizationl as a result of addition to the initially formed valence isomer (3.38). A different kind of photoaddition occurs when benzenes react photochemically with amines cyclohexa-T, 4-dienes are the major products (3.39), accompanied by cyclohexa-1.3-dienes, and unlike many of the photochemical reactions of benzene this does not suffer loss of efficiency in scaling-up. 

By extension uf the reactions involved in the formation of cyclopolysilanes. West and Carbeny"7 synthesized bicydic and cugc permcthylpolysilanes such as ... 

The bicydic meso-ionic 3-oxo-l,2,4-triazolo[4,5-a]pyridines (206) have been prepared by the following methods (i) the reaction of the hydrazines (207, X = H) with phosgene,138,139 (ii) heating the amide (207, X = CONHj) or the carbamate (207, X = C02Et),136 and (iii) alkylation or acylation of 3-oxo-l,2,4-triazolo[4,5-a]pyridine (208).133 The isomeric meso-ionic 2-oxo-l,3,4-triazolo[4,5-a]pyridines (209) are formed from the carbamoyl chlorides (210) and sodium azide.140... 

Leonetti, J. A. Gross, T. Little, R. D. Cycloaddition-fragmentation as a route to bicydic ring systems. Use of the intermolecular diyl trapping reaction./. Org. Chem. 1996, 62, 1787-1793. 

Bicyclic alkenes like 64 and 65 (Scheme 13) also undergo stereoselective migration. The bicydic olefin 64 reacts similarly to the substituted cydopentenes at 50 °C within 3h affording alcohol 68 in 82% yield after oxidative workup (Scheme 13). The six-membered bicyclic system 65 reacts much more slowly and requires 7 h reaction time at 70 °C, affording, after oxidative workup, the alcohol 69 in 72 % yield (Scheme 13) [6-8]. 

The Norrish-Yang reaction, with the spin-center-shift extension, facilitates access to a variety of cyclic compounds. This will be discussed here, with examples of the synthesis of three- to six-membered rings synthesis of macro- and bicydic compounds and the photochemistry of imides will not be covered. The examples especially demonstrate the capabilities of the reaction with regard to stereoselectivity. 

With respect to this, Ellman and coworkers [16], Zhu and coworkers [17], Amusch and Pieters [18], and Liskamp and coworkers [19] have prepared (monocyclic) mimics of the D-E part of the cavity of these antibiotics via an intramolecular nucleophilic aromatic substitution [16-18] or a Sonogashira-based macrocyclization [19] (Figure 1.4). Recently, a bicydic mimic of the C-D-E cavity, which was prepared by a Stille reaction followed by tandem ring-dosing metathesis (9, Figure 1.4), was described by liskamp and coworkers [20]. Considerable challenges lie ahead for the synthetic chemist in order to develop practical syntheses of mimics of vancomydn capable of binding not only D-Ala-D-Ala, but also cell wall parts of resistant bacteria, i.e. D-Ala-D-lactate. 

A highly exo-selective formation of bicydic oxetanes was also observed during the PB reaction with oxazole derivatives [38] and vinylene carbonate [39] (Scheme 7.21). 

The stereoselective formation of bicydic oxetanes was also reported in the PB reactions of diketones (Scheme 7.22). Here, Mattay and Griesbeck reported the endo-selective formation of oxetanes in the PB reaction of 1,3-dioxol derivatives with some methyl pyruvates [40]. The PB reaction ofarylglyoxylates with furan was also found to produce stereoselectively the bicydic oxetanes (Scheme 7.23) [41]. Neckers and coworker demonstrated the highly efficient formation of oxetanes in the intramolecular PB reaction (Scheme 7.24) [42]. 

Abe, M., Taniguchi, K., and Hayashi, T. (2007) Exo-selective formation of bicydic oxetanes in the photocydo-addition reaction of carbonyl compounds with vinylene carbonate the important role of intermediary triplet diradicals... 

Clennan, E.L. and Heah, P.C. (1984) Bicydic dioxaphosphorane. 4. A kinetic investigation of the reactions of trivalent phosphorus compounds with bicydic endoperoxides. Journal of Organic Chemistry, 49, 2284—2286. 

The 3-aminomethyl-l-pyrrolidinyl radical, which was considered to be bioiso-steric to piperazine [91], also produced highly active quinolones, which were however also found not to be tolerated. In trovafloxacin 16 [92], the 3-aminomethyl-l-pyrrolidinyl radical is integrated into a bicydic amine structural unit with a free amino group [(la,5a,6a)-6-amino-3-azabicyclo[3.1.0]hexane]. A correlation probably exists between the increased central nervous system (CNS) side effects obtained with this quinolone [93] and the 2,4-difluorophenyl radical in the 1-posi-tion. Severe hepatic intolerance reactions finally resulted in major restrictions on its use, which was then limited in the USA to severe clinical infections [68]. 

Baeger-Villiger reaction, 311 Barbiturates, 358 Base peak in ms. 248 Bases, soft and hard. 121 Basicity and structure. 43 Basic Red. 428 Beckmann rearrangement. 406 Benzene, resonance structure. 192 structure, 189 Benzenonium ion, 205 Benzhydrol, 269 Benzidine rearrangement. 422 Benzyne. 217 Bicydic compounds. 162 Birch reduction, 200 Bischler-Napieralski reaction, 460 Boat and chair forms. 168 Boiling point, influences on, 212 Bond dissociation, 37 Bond order, 17 Bond stretching. 233 Bonding orbitals, 14 Bredt s rule. 168 Bromonium ion. 100 BrOnsted. 42... 

---