Tosyl ring closures with

Allyl p-tolyl sulfone and tetramethylammonium chloride in methanol cooled to 5°, then electrolyzed with a Hg-cathode and water as anolyte at 18-24 V and 1 amp. until after 30-35 min. vigorous Hg-evolution indicates completion of the reaction p-toluenesulfinic acid (Y 80%) and propylene (Y 75%). F. e. s. L. Horner and H. Neumann, B. 98, 1715 (1965) also selective removal of protective groups from peptides s. B. 98, 3462 (1965) with tetramethylammonium tosylate, ring closures by intramolecular electrolytic reduction of activated dienes s. J. D. Anderson and M. M. Baizer, Tetrah. Let. 1966, 511. 

Trifluoroacetic acid 5. under 3-Methylbenzothiazole-2-selone Dimethyl sulfoxide Ring closure with tosylates l,2,3,3a,4,5,8,8a-Octahydro-2,5-methanoazulenes... 

The original method (A) involves conversion of the bis-tosylate to the cyclic diselenide followed by reduction of the Se-Se bond and ring closure with sulfur monochloride (eq 1). This method was recently improved in both yield and simplicity using a sulfur insertion methodology (path B, eq 1). ... 

Potassium/tert-butanol N-Ring closure with tosylates... 

Thus, 5-methoxypyrimidine 103 when treated with lithium tetramethylpiperidide (LTMP) and subsequently by tosyl azide led to formation of the 2-azido derivative 104, which spontaneously undergoes ring closure to 8-methoxytetrazolo[l,5-c]pyrimidine 105. 

Axenrod and co-workers reported a synthesis of TNAZ (18) starting from 3-amino-l,2-propanediol (28). Treatment of (28) with two equivalents of p-toluenesulfonyl chloride in the presence of pyridine yields the ditosylate (29), which on further protection as a TBS derivative, followed by treatment with lithium hydride in THF, induces ring closure to the azetidine (31) in excellent yield. Removal of the TBS protecting group from (31) with acetic acid at elevated temperature is followed by oxidation of the alcohol (32) to the ketone (33). Treatment of the ketone (33) with hydroxylamine hydrochloride in aqueous sodium acetate yields the oxime (34). The synthesis of TNAZ (18) is completed on treatment of the oxime (34) with pure nitric acid in methylene chloride, a reaction leading to oxidation-nitration of the oxime group to em-dinitro functionality and nitrolysis of the A-tosyl bond. This synthesis provides TNAZ in yields of 17-21 % over the seven steps. 

Treatment of the tosylate 18 with LDA furnished a 97 3 mixture of the cyclobutanecarboxylates 19 and 20 in 45% yield. This ring closure succeeded in 65% yield even when potassium hexamethyldisilazanide was used103, although the selectivity dropped slightly to 95 5. 

Enantiomerically pure pipecolic acid (6) is accessible essentially by two well-established synthetic routes (i) cyclization of l- or D-lysine by reaction with disodium nitrosyl-pentacyanoferrate(II) with preservation of configuration at C2 215 216 (ii) ring closure of A ,Ae-bis(A-nitroso-A-tosyl) derivatives of l- or D-lysine, again with retention of chirality at C2. 217 Stereoselective synthesis of pipecolic acid derivatives, substituted in position 4, is achieved using the aza-Diels-Alder reaction of imines with dienes 218-220 or via an ene-iminium cyclization. 221 222 ... 

Although not competitive synthetically with the methods discussed above two interesting applications of ring closure reactions for the synthesis of homoadamantane derivatives have been reported. The first involves trans-annular cyclopropyl participation in the solvolysis of 48 acetolysis gives 3-homoadamantyl acetate as the only observed product (Eq. (32)) 112 Comparison of the acetolysis rate of 48 (2.14 x 10 4 sec"1,25°C) with that of exo-3-bicyclo[3.3.1]nonyl tosylate (5.82 x 10"s sec. 1,25°C) U3>114)... 

Taking into account the vicarious nature of the nucleophile the authors suggested that ring closure occurs inside alkenic aH-adduct 290 with participation of the nitro group. However, in principle, the reaction might proceed via the formation of nitroso compound 291 with subsequent electrocyclization into oxazine 292 and hydrolytic exchange of the p-tosyl group (Scheme 85). 

In principle, any compound prepared by a ring-closure reaction in Section 14.11.5.3 and substituted with a removable substituent on ring nitrogen atoms can serve as a protected cycle. This is particularly true of a full range of the cyclic amides and sulfonamides (mostly tosylamides). Examples of the approach are 172 and 173 prepared by the tosylate method from tosylated and benzylated precursors <1995T1197>. Protected 16-membered tram 1,9-dibenzyl-l,5,9,13-tetraazacyclohexadecane was also obtained in this way <1998SC285>. 

Derivatives of 1-methyl-3//-l,4-benzodiazepine-2,5(l/I,4/I)dione (193) were synthesized by ring closure of substituted 2-(A-chloro-acetyl-A-methylaminoJbenzamides with sodium methoxide in methanol.209 Treatment of 193 with lithium aluminum hydride led to reduction of both carbonyl groups.209 The parent tetrahydro system (194) has been prepared by reaction of the tosylate (195) with 1,2-dibromoethane followed by hydrolysis.210 The preparation of 194 by another route had previously been noted.204 Reaction of 194 with formaldehyde or benzaldehyde gave a compound formulated as 196 (R = H or C6H5).210 Hydrolysis of 196 (R = C6H5) with 0.1 N hydrochloric acid gave 194 while 196 (R = H) was not hydrolyzed at this acidity. 

---