Naphtho thiete

Naphtho-thietes, 21 151 Naphtol products, 9 281 1-Naphthylacetic acid derivatives, 12 176 1-Naphthyl chloroformate, molecular formula, 6 291t... 

Meinwald and coworkers71 studied the chemistry of naphtho[l, 8-bc]thiete and its S-oxides. The reaction of the sulphone 2 with LAH (equation 29) is of particular and direct relevance to this section since it is different from the reductions that have been discussed thus far, because the major reaction pathway is now cleavage of an S—C bond, rather than a deoxygenation of the sulphur atom. The major product (equation 29) was isolated in 65% yield two minor products accounted for a further 15% yield. One of the minor products is 1-methylthionaphthalene and this was most probably produced by an initial reduction of the strained 1,8-naphthosulphone, 2, to the thiete, which was then cleaved to the thiol and subsequently methylated. Meinwald also showed71 that the thiete was subject to cleavage by LAH as well as that both molecules were susceptible to attack and cleavage by other nucleophiles, notably methyllithium. These reactions are in fact very useful in attempts to assess a probable mechanism for the reduction of sulphones by LAH and this will be discussed at the end of this section. 

It is intriguing to note that this reaction scheme for the reduction of a sulphone to a sulphide leads to the same reaction stoichiometry as proposed originally by Bordwell in 1951. Which of the three reaction pathways predominates will depend on the relative activation barriers for each process in any given molecule. All are known. Process (1) is preferred in somewhat strained cyclic sulphones (equations 22 and 24), process (2) occurs in the strained naphtho[l, 8-hc]thiete 1,1-dioxide, 2, cleavage of which leads to a reasonably stabilized aryl carbanion (equation 29) and process (3) occurs in unstrained sulphones, as outlined in equations (26) to (28). Examples of other nucleophiles attacking strained sulphones are in fact known. For instance, the very strained sulphone, 2, is cleaved by hydride from LAH, by methyllithium in ether at 20°, by sodium hydroxide in refluxing aqueous dioxane, and by lithium anilide in ether/THF at room temperature. In each case, the product resulted from a nucleophilic attack at the sulphonyl sulphur atom. Other examples of this process include the attack of hydroxide ion on highly strained thiirene S, S-dioxides , and an attack on norbornadienyl sulphone by methyllithium in ice-cold THF . ... 

Flash vacuum pyrolysis has been used in the synthesis of 2ff-naphtho[l,2-f>]thiete 8 <98JHC1505> and benzobisthietes 9 and 10 <98TL9639>, and their Diels-Alder cycloaddition reactions have been studied. 

Eight-membered ring disulfone (181) <67LA(703)96) is reported to undergo conversion to naphtho[ 1,8-bc ]thiete 1,1-dioxide upon UV irradiation. 

Naphtho[ >, c]thiete (75) was obtained with high yield as a stable compound on photolysis of (74) or (76). Nitrogen and oxygen analogues of (75) are unstable, but can in some instances be trapped. 

A4-Naphtho[l,8-6c]thiete 1-oxide 13C NMR, 7, 415 (76JA6643) Naphtho[2,3-b]thiophenium, l-methyl-X-ray, 4, 724 (81JA289)... 

Unlike naphtho[6c]oxete, described previously, its thio analog 20 is a stable compound which can be obtained in high yield (97-100%) on photolysis of naphtho[c[Pg.8]

IJOC4570). Photolysis or thermolysis of naphtho[ c]thiete 20 and naph-tho[carbon disulphide, also occurs by a free-radical mechanism which leads to naphtho[other products of these conversions [79JA7684 81JCS(P1)413]. 

The reactivity of the benzo analogue of compound 41, that is, 2//-naphtho[l,2-4]thiete 47, has also been studied. Cycloaddition reactions with dienophiles or heterodienophiles performed in boiling toluene yielded naphtho-condensed sulfur heterocycles (Scheme 5) <1998JHC1505>. 

Three isomers — 2//-naphtho[ 1,2-/dthiete 47, 1 //-2-naphtho[2,l -3]thiete 48, and 2//-1 -naphtho[2,3-7 ]thiete 49 -obtained in situ from 3-oxoH//-3,l-naphtho[l,2-z/]oxathiin, 3-oxo-l A/-4,2-naphtho[2,1 -z/]oxathiin, and 2-OXO-4//-3,1-naphtho[2,3-z/]oxathiin, respectively, were subjected to reaction with dimethyl or diethyl fumarate. Refluxing a solution of the corresponding precursors in toluene (for 49 in diethyl fumarate at 200 °C ) in the presence of... 

An x-ray structural analysis has been done on thiete 1,1-dioxide (248), naphtho[l,8-bc]thiete 1,1-dioxide (205b),and rrans-2,5-dibromo-7-thiabicyclo-[4.2.0]-l(6)-octene 7,7-dioxide (249). A microwave spectrum of thiete sulfone has been obtained for which an O-S-0 angle of 120.1° was preferred, which differs from the value of 115.5° found in the x-ray analysis. 

A different approach was used for the synthesis of the naphtho[ 1,2]thiete 1,1-dioxide 272. The peri-naphthothiete sulfone 20Sb is prepared by photolysis Qf 271612.613 oxidation of the sulfide 205. = ... 

The sulfur-sulfur interatomic distance in 9-phenyl-4,8,10-trithiadibenzo[cd,ij]a-zulene-8-oxide (417) is significantly shorter than the sum of their van der Waals radii and photolysis of (417) and (418) yields (420) and aldehydes or ketones (421) quantitatively. The unstable primary photoproduct (419) may be isolated and photolyses to (420) and (421). A similarly short sulfur-sulfur interatomic distance is found in a series of naphtho[l,8-ef][l,4]dithiepins and direct irradiation yields naphtho[l,8-cd][l,2]dithioles quantitatively with analogous S-S bond formation and alkene elimination. Photolysis of compounds (422), (424) and (426) gives the dimerised disulfides (423), (425) and (427) in 45%, 17% and 1% yields respectively. Irradiation of the tetraalkyl-2H-thietes (428) at 254 nm leads to a photostationary mixture containing the purple enethiones (429) (25%). Exposure of the mixture to 300 nm radiation induces almost complete reversion to (428). ... 

Figure 7. General formulas, bond angles in the hetero ring, and other calculated parameters of naphtho[l,8-i/c]thiete and its V-oxides...

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