3-p-Menthol

SYNS FEMA No. 2665 4-ISOPROPYL-l-METHYL-CYCLOHEXAN-3-OL dl-3-p-MENTHANOL 3-p-MENTHOL MENTHOL racemic MENTHOL racemique (FRENCH) 5-METHYL-2-(l-METHYLETHYL)-CYCLOHEXANOL (l-0,2-P,5-a)... 

Piperitone is of considerable technical im portance. It is a colourless oil of a pleasant peppermint-like smell. (-)-Piperilone has b.p. 109-5-110-5 C/I5mm. Piperitone yields thymol on oxidation with FeCl. On reduction with hydrogen in presence of a nickel catalyst it yields menthone. On reduction with sodium in alcoholic solution all forms of piperitone yield racemic menthols and womenthols together with some racemic a-phel)andrene. 

Menthol can also be synthesized from optically active terpenoids such as (+)-citroneUal, (-)- P-pheUandrene, and (+)-3-carene. The synthesis from (+)-3-carene has already been discussed in the section on hydrocarbons. Such methods must avoid any racemization during the course of a usually multiple-step synthesis. One disadvantage of such methods is that the other menthol diastereoisomers must be equilibrated and recycled. 

French oil of peppermint eontains. in addition to menthol and iia, isovaleric aldehyde, isoamyl alcohol, i-pinenc. A -p-monthcne aed... 

Chiral alcohols have also been used in an asymmetric synthesis of sulphoxides based on halogenation of sulphides. Johnson and coworkers have found319 that the reaction of benzyl p-tolyl sulphide with JV-chlorobenzotriazole (NCBT) followed by addition of (—) menthol and silver tetrafluoroborate afforded diastereoisomeric menthoxysulphonium salts 267 which, upon recrystallization and hydrolysis, gave benzyl p-tolyl sulphoxide with 87% optical purity (equation 145). More recently, Oae and coworkers reported320 that optically active diaryl sulphoxides (e.e. up to 20%) were formed either by hydrolysis or thermolysis of the corresponding diaryl menthoxysulphonium salts prepared in situ from diaryl sulphides using ( —) menthol and t-butyl hypochlorite. 

As an alternative, Harpp and coworkers reacted benzenesulfinyl chloride with the trimethylsilyl derivative of menthol to form the diastereomeric esters in 91% yield the epimer of configuration R could be isolated by crystallization in unspecified yield. Grossert and coworkers prepared ester 19 in 51% yield as a mixture of diastereomers by treating p-toluenesulfonyl chloride with sodium p-toluenesulfinate in DMF containing menthol. It was postulated that initial nucleophilic attack by the sulfinate oxygen on the sulfonyl sulfur atom gave the mixed sulfonate-sulfinate anhydride 21, which then reacted... 

A 5-1. three-necked round-bottomed flask is fitted with a mechanical stirrer (Note 1) and a reflux condenser bearing a calcium chloride tube. A solution of 400 g. (2.56 moles) of -menthol (crystals, m.p. 41-42°) in 11. of dry toluene (Note 2) is placed in the flask, and to it is added 70 g. (3.04 gram atoms) of clean... 

Esterification of p-toluenesulfinic acid with (- )-menthol gives a mixture of two diastereomers, which equilibrate to the pure (-)-menthyl (S)-p-toluenesulfinate diastereomer in the presence of hydrochloric acid (80% yield). The report includes an improved procedure for reaction of 1 with CH,MgI to give (R)-( + )-methyl p-tolyl sulfoxide.1... 

P-parinaric acid, physical properties, 5 33t P-pentenoic acid, physical properties, 5 3 It P-peroxylactones, 18 484 Beta phase titanium, 24 838 in alloys, 24 854-856 properties of, 24 840, 941 P-phellandrene, 24 493 P-picoline, 21 110 from acrolein, 1 276 uses for, 21 120 P-pinene, 3 230 24 496-497 major products from, 24 478 /-menthol from, 24 522 as natural precursor for aroma chemicals, 3 232 terpenoids from, 24 478-479 P-propiolactone, polymerization of, 14 259 P-quartz solid solution, 12 637—638 Beta ratio, in filtration, 11 329—330 Beta (P) rays, 21 285 P-scission reactions, 14 280-281 P-skytanthine, 2 101 P-spodumene solid solution, 12 638-639 P-sulfur trioxide, 23 756 P-sultones, 23 527 P-tocopherol, 25 793 P-tocotrienol, 25 793 P-vinylacrylic acid, physical properties, 5 33t... 

Chiral sulfinates are important intermediates that are widely applied in the synthesis of other classes of chiral organosulfur compounds and in their configurational correlations. Optically active sulfinates were first prepared in 1925 by Phillips (100) in two ways. The first consisted in the transesterification of racemic alkyl p-toluenesulfin-ates with chiral alcohols such as (-)-menthol and (-)-2-octanol yielding a mixture of two optically active sulfinates as shown in eq. [26]. The... 

In addition to sulfimides, the nitrogen analogs of sulfinates and sulfinamides are chiral and have been obtained as optically active compounds. For instance, the synthesis of diastereomeric menthyl p-toluenesulfinimidoates 90 mentioned above was effected by Cram and his collaborators (18,137) on two ways. The first comprised the reaction of racemic A -tosyl-p-tolueneiminosulfinyl chloride 92 with menthol, followed by separation of the diastereomers of 90, whereas in the second method the reaction of the ester (->45 with chloramine T was utilized. 

Quite recently, an asymmetric synthesis of alkoxyaminosulfonium salt 122 and diaminosulfonium salt 125 was accomplished (163) by way of menthoxysulfonium salt 126, obtained by treating A -p-toluene-sulftnylmorphoUne with 1-chlorobenzotriazole (NCBT), followed by menthol. The subsequent addition of methanol and sodium tetra-phenylborate gave the optically active salt 122 (Scheme 7). When 126 was treated with piperidine instead of methanol, the optically active diaminosulfonium salt 125 was formed. 

---