Harutoshi Matsumoto

THERMAL REARRANGEMENT OF 9-BENZYL-10-AZA-9-THIAPHENANTHRENES

Abstract 9-Benzyl-10-aza-9-thiaphenanthrenes ( 3 ) generated from 9-benzyl-10-aza-9-thiaphenanthreniun salts ( 2 ) by treatment with base underwent thermal 1,2-benzyl migration to give the corresponding 6-benzyl-6H-dibenzo[c,e][1,2]thiazines ( 4 ).

Pummerer reaction of 2-vinylcyclopropyl sulfoxides: generation and reactions of butadienylthionium ion intermediates

Generation of butadienylthionium ions in the Pummerer reactions of 2-vinylcyclopropyl sulfoxides has been investigated. Although the Pummerer reactions of 2-vinylcyclopropyl sulfoxides 1 are complicated, benzothiazinone derivatives 10 smoothly react with trifluoroacetic anhydride to give 1,3-dienes in good yields. The reactions proceed via butadienylthionium ions by proton abstraction from the 2′-methyl group or the cyclopropane ring. Reactions of disubstituted benzothiazinones 10e–h provided cyclic dienes while treatment of mono- or un-substituted derivatives gave acyclic conjugated dienes 11a–d. 2-Vinylcyclopropyl sulfoxides 1 and 10 were prepared by MCPBA oxidation of the corresponding 2-vinylcyclopropyl sulfides 19 and 23, respectively, which were obtained by cyclopropanation of α-chloro sulfides with 1,3-dienes via the 5,6-dihydro-2H-thiopyranium intermediate 22.

Acid-promoted isomerisation of 1-acceptor-1-sulfenyl-substituted2-vinylcyclopropanes with C1–C2 bondfission and novel 1,5-sulfenyl rearrangement

1-Acceptor-1-sulfenyl-substituted vinylcyclopropanes 1 undergo C1–C2 bond fission and 1,5-sulfenyl rearrangement to give 6-sulfenyl-α,β;γ,δ-unsaturated carboxylic esters and nitriles 4 by treatment with acid. The reactions proceed smoothly by use of a sulfonic acid such as p-TsOH·H2O, CF3SO3H etc. in a non-polar solvent. The results, obtained from reactions of compounds 12 and 16, imply that the C1–C2 bond cleavage and deprotonation from the C2-methyl group of substrates 1 occur via a concerted process. The cross-over experiment showed that the 1,5-sulfenyl shift proceeds intermolecularly. Addition of a catalytic amount of m-MeC6H4SH improves the yield of the rearranged product 4c.

Synthesis and reactions of lactam sulfonium salts with a sulfoniobridgehead. Part 1.4,4a,5,6-Tetrahydro-5-oxo-1H-thiopyrano[1,2-a]-1,4-benzothiazinium perchlorates

Tricyclic benzothiazinium salts 3 are prepared by [2++4] polar cycloaddition of thionium intermediates 2A, generated from the corresponding α-chloro sulfides 2, and dienes in the presence of silver perchlorate. Ring transformation of benzothiazinium salts 3 with a reducing agent such as Mg, NaBH4 and Zn–AcOH or with a base, furnishes spiro-vinylcyclopropane derivatives 4 in moderate to high yields. Electrolysis of 3a at -1.4 V vs. SCE in acetonitrile also affords vinylcyclopropane 4a (60%). These results indicate that both ionic and radical mechanisms may account for the vinylcyclopropane formation, although it is unclear as to the nature of the radical intermediate. The stereochemistry of 4a was determined by X-ray analysis showing that sulfur and the vinyl group are cis-orientated. Ten-membered lactam sulfides 6 are obtained as the major product of SmI2 reduction of 3.

Generation and reactions of butadienylthionium ions from 2-vinylcyclopropyl sulfoxides under Pummerer conditions

Treatment of 2-vinylcyclopropyl sulfoxides lacking an α-hydrogen with acid anhydrides produced butadienylthionium ion intermediates to give cyclic or acyclic conjugated dienes.

Syntheses and thermal behaviour of 9-substituted 9-thia-10-azaphenanthrenes

Synthetic approaches to a variety of 9-thia-l0-azaphenanthrenes having various kinds of substituent at the 9-position were investigated. Their thermal stabilities were found to depend strongly upon the nature of the substituents on the sulphur atom. Several 9-alkyl and 9-phenyl derivatives are quite stable at room temperature; in particular, the phenyl derivative was too stable to undergo thermal degradation. Refluxing in xylene for many hours effected some change of the 9-phenyl derivative 7ab to result in the formation of 1,4-rearranged 11 and N–S bond-cleaved 3ab products, while 9-alkyl derivatives 3c–3f were easily decomposed in refluxing benzene to undergo β-elimination to give 6H-dibenzo[c,e][1,2]thiazine 9 as major product. 9-Benzyl, 9-(4-substituted benzyl), 9-fluoren 9-yl and 9-cyanomethyl derivatives underwent, even at below room temperature, 1,2-rearrangement of the 9-substituent to afford the corresponding 6-substituted 6H-dibenzo[c,e][1,2]thiazines 10g–10o, 10w, which are very rarely observed in sulphilimine chemistry. A 9-silyl-group-substituted derivative was also too unstable to be isolated and caused a 1,2-imino shift to give the ringexpanded product 18. 9-Acylmethyl derivatives underwent Sommelet–Hauser-type rearrangement to afford benzothienoindole derivatives 24.