Azides transannular

In an earlier study the authors proposed a [3.2.0] bicyclic sulfonium salt 8 as the reactive intermediate in the trimethylsilyl iodide mediated ring contraction of 4-methoxythiephane <1996T5989>. Enantiomerically pure thio-lane derivatives were synthesized via a ring contraction of a seven-membered sulfur heterocycle by nucleophilic transannular substitution <2000TA1389>. The thiepane derivative 15, derived from d-sorbitol, was converted into the dimesyl derivative 16 following deprotection under acidic conditions. Treatment of 16 with sodium azide in DMSO at 120°C yielded the corresponding thiolane as a mixture of two diastereoisomers, 17a and 17b, in a 5 1 ratio (see Scheme 1). 

Chang et al. reported a mild tandem intramolecular hydroamination of yne amines to form an endo-adduct intermediate, which reacts with electron-deficient azides to produce cyclic amidines <06JA12366>. Selected examples of an interesting synthetic route to tropene derivatives 165 via a dual hydroamination strategy is shown below. This one-step reaction makes use of a palladium catalyst and takes place by sequential intermolecular hydroamination of cycloheptatriene with aryl, heteroaryl, and primary alkyl amines to generate intermediate 166, followed by transannular intramolecular hydroamination <06JA8134>. 

Significant amounts of the bicyclo[3.3.1]nonane adduct and of the octahydropental-enes were isolated also from the reaction of 3 with preformed iodine acetate and iodine acetate thallium (equation 75)94 whereas only the monocyclic 1,2-adducts were obtained from treatment of 3 with iodine azide, iodine isocyanate or iodine nitrate95. The different propensity to give transannular products with these latter reagents has been related to the different positive charge density on carbons in the corresponding iodonium ion intermediates. 

Elimination of HI, which in the presence of an excess of IN3 can form hydrazoic acid, followed by its addition to the vinyl azides can give an intermediate triazide 75. The same compound could arise directly by substitution of one iodine atom by an azido group. The intermediate 75 has been considered to undergo a transannular reaction with homolytic cleavage of the weak C—I bond to form the radical 76, which loses a nitrogen atom to a radical 77. Combination of the two radicals leads to the 2-tetrazene 74 (equation 77). 

Formation of cluster opened methano- and imino[60[fullerenes (fulleroids and azafUlleroids) Thermal [3+2]-cycloadditions ofdiazo compounds or azides leads to the formation of fulleropyrazolines or fullerotriazolines. Thermolysis of such adducts after extrusion of N2 affords as kinetic products the corresponding [5,6]-bridged methano and iminofullerenes with an intact 60 re-electron system and an open transannular bond (see Chapter 4) [88-91]. The corresponding [6,6]-bridged structures with 58 re-electrons and a closed transannular bond are formed only in traces. 

Irradiation of the pyrazoline mixture 12, 13, and ( )-14 yielded methanofullerenes 15 and 16 (7 1) with a closed transannular 6 - 6 bond besides minor amounts of a third constitutional isomer (17), whereas thermolysis of the same mixture gave 17 and inherently chiral ( )-18 (4 l),both constituting core-modified fullerenes [76] (Scheme l).With open transannular 6-5 bonds , the functionalized regions of 17 and ( )-18 resemble methanoannulene sub-structures. [3 + 2]Cycloaddition of alkyl azides to C70 affords triazolines which are isolable when the temperature does not exceed ca. 50 °C. Similar to the reaction with diazomethane, three constitutionally isomeric adducts were observed [77,113], and the regioisomer of type 19 [113] with the substituent of the heterocycle located above the apex of C70, predominated over its regioisomer of type 20 in two in-... 

The natural a-glucosidase inhibitor salacinol (9) (see Vol. 31, p. 163, ref. 29) and its diastereomer 10 have been synthesized by opening of the cyclic sulfates 8 and its 1,3-cyclic sulfate equivalent, respectively, with l,4-anhydro-4-thio-D-arabinitol. On treatment with NaNs in DMSO the thiepane 11, readily available from D-glucitol, underwent direct Sn2 substitution of one of the mesylate groups by azide, while the other mesylate group was diplaced transannularly by sulfur. Attack of Ns on the the resulting bicyclic sulfonium salts aiforded a 5 1 mixture of l,4-anhydro-4-thio-hexitols 12 and 13. ... 

The chemistry of l-methyl-truns-cyclo-octene has been studied. In particular it reacts with acidic methanol to give 1-methoxy-l-methylcyclo-octane, with bromine to give a complex mixture, and with peracid to give its epoxide. On warming in acetic acid it is isomerized to 1-methyl-cis-cyclo-octene, and it reacts with diazomethane and phenyl azide to give cycloaddition products. With 4-phenyl-1,2,4-triazine-3,5-dione, the ene product (121) is obtained. The major difference in reactivity between trans-cyclo-octene and its 1-methyl analogue was found for electrophilic addition reactions where the stability of the incipient 3° cation made the 1-methyl compound more reactive.Transannular products were obtained from the reaction between trans-... 

The second one-pot cascade reaction was used to complete the synthesis of the natural product from acid 69. Reduction of the two azide groups of 69 produced the highly polar diamine 70, which was treated with EDC and HOBt to induce an intramolecular lactam cyclization and deliver the macro-palau amine 71. When the crude reaction mixture of 71 was heated in TEA, compound 72, proceeding through amidine tautomer 71, elicited the key transannular cyclization and delivered the palau amine in 17% overall yield from 69. The outcome stereochemistry was all in the control of the stereocenters within the substrate. 

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