2- bromo Open-Chain Compound

As a consequence of the cyclobutyl to homoallyl rearrangement, reactions of 1-chloro-, 1-bro-mo-l,2-dimethylcyclobutane, 1-chloro- or l-bromo-l,3-dimethylcyclobutane with silver(I) te-trafluoroborate in diethyl ether gave in each case the same open-chain compound 2-fluoro-4-mcthylpent-4-ene (14) as the major product. Thus, l-bromo-l,3-dimethylcyclobutane (13) was treated with silver(l) tetrafluoroborate in diethyl ether at 0 >C to give 2-fluoro-4-methylpent-4-ene (14).22... 

In open-chain compounds, where rearrangement products are more easily obtained, 2-bromo-2,4-dimethyl-3-pentanone gives the a-alkoxyketone as a major product even when the reaction is carried out under aprotic conditions.Consequently two factors seem to be decisive in inhibiting cyclopropanone formation and yielding the a-alkoxyketone even in an aprotic solvent. The first is the degree of substitution, which can play a role in open-chain or cyclic compounds. The second operates only in cyclic systems and is ring strain which can be calculated by force field techniques. This kind of strain can be due to valence angle deformations or to transannular nonbonded interactions or bonded interactions. ... 

A number of 1,2,4-triazines such as the parent compound, the 3-methylthio, 3-methoxy and 3-amino-6-bromo derivatives add ammonia in liquid ammonia at -44 °C to the N(4) —C(5) bond to give adducts of type (lOl), as was shown by XH and 13CNMR spectroscopy. No reaction was observed with 3-methoxy-l,2,4-triazine 1-oxide (71), other 3-amino-l,2,4-triazines, or compounds with a substituent in the 5-position. As was shown using lsN-enriched ammonia, an equilibrium between the covalent addition products (101) and the open-chain isomers (102) does not occur (78RTC273). 

It has to be noted that 97 and 98 could not be obtained, by a biomimetic way, i.e. oxidative cyclization of the corresponding open chain phenols 137 and 138 respectively. In contrast the bromo compound 157 prepared from 154 could be induced to undergo photocyclization yielding a mixture of myricanone and its mono and dibenzyl ethers. 

For L-isopropylidene-DHA, D-isopropylidene isoDHA, and 6-bromo-6-deoxy-L-DHA, the assigned shifts for C2 and C3 are upfield from values expected for keto groups. This observation indicates that these carbons are hydrated. In these compounds the C6 hydroxy group has either been derivatized or replaced, preventing the formation of the hemiketal. These compounds readily form an open-chain form of DHA, suggesting a reasonable stability for the hydrated diketo structure. 

A noteworthy difference is observed in the condensation of thiosemicarbazide with aromatic a-halocarbonyl compounds in comparison to aliphatic a-halocarbonyl compounds. It has been found26 that the reaction of phenacyl bromide with thiosemicarbazide furnishes 5-phenyl-1,3,4-thiadiazin-2-amine together with a small amount of 5-phenylthiazolc-2-hydrazine, Similarly, the reactions of thiosemicarbazide with 2-bromo-l,2-diphenylethan-l-one,7 8,41 2-bro-mo-l-phenylpropan-l-one,10,41 and 2-bromo-l-phenylbutan-l-one 10,41 in ethanolic solution give 1,3,4-thiadizines. However, the main products are the thiazole-2-hydrazine derivatives (cf. Houben-Weyl, Vol. E8b, p 72ff). The addition of an equimolar amount of 48% hydro-bromic acid results in the exclusive formation of the 1,3,4-thiadiazines 2 a, c, and d. When the condensations of thiosemicarbazide with 2-bromo-l,2-diphenylethan-l-one, 2-bromo-1-phenylpropan-l-one or 2-bromo-l-phenylbutan-l-one are performed in ethanol at room temperature, the S-(oxoalkyl)-isothiosemicarbazide hydrobromides are formed as open-chain intermediates and also undergo cyclization in ethanol upon addition of an equimolar amount of 48% hydrobromic acid to furnish 2 a, c, and d. 

Construction of a side-chain onto 6-bromo-2-naphthol allows the formation of naphtho[2,l-b]furan-6-ols and hence furo[3,2-/]naphtho[2,l-b]pyrans 47. Compared with the analogous 8-methoxynaphthopyran, > ax for both the closed and open forms of these compounds are further to the red. The intense colouring molecules have half-lives of the order of 2 minutes <95USP5674432>. 

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