SOME INVESTIGATIONS OF THE CHEMISTRY OF CARENE 267 (formula 45) which was obtained by the lithium aluminium hydride re- duction of (--)-trans-caran-2-one (formula 13), gave (+)-trans-p-mentha- 2,8-diene (formula 46) (85%) and (+)-p-mentha-2,4(8)-diene (formula 41, R, a- CH 3) (15%). 9 '0 ' (45) (4•) (47) OH (48) On heating (--)-trans-caran-cis-2-ol (formula 45) with a little acetic acid in a sealed tube at 210øC, (+)-trans-p-mentha-2,8-diene (formula 4t3) was again the predominant product. Its spectra (Table IV) and the fact that on hydrogenation it affords trans-p-menthane largely settle its structure. However the configuration of the 7- methyl group follows from the con- figuration of the alcohol (formula 45), since this methyl takes no part in the reaction. If it did, the pyrolysis product would be p-mentha-1,8-diene (for- mula 47). The minor product of the acid-catalysed thermal isomerisation was (+)-trans-p-menth-2-en-8-ol (formula 48) (33) an analogous alcohol to (--)-cis-m-menth-4-en-8-ol (formula 131) similarly formed from (+)-cis- caran-cis-5-ol (formula 213). The infra-red spectrum of the menthenol (for- mula 48) showed peaks at 13350 (OH), 1 1350 (C=C), and 728 (cis CH=CH) cm-1, whilst its nmr spectrum had signals at z 9.04 (d, J 13Hz, CCH3), 8.86 and 8.91 [singlets, C(CH 3) 2], 8.213 (s, OH) and 4.138 (s, H2,13). Its mass spectrum was similar to that of its isomer (formula 131) (see above). These spectra confirm its structure. Larger yields (85%) of (+)-trans-p-menth-2-en-8-ol (formula 48) were obtained when (--)-trans-caran-cis-2-ol (formula 45) was treated with 13N hydrochloric acid. a-Terpinene (formula 40) (5%) and (+)-p-menth-2,4(8)- diene (formula 41 R, a-CH 3) (15%) are other products of this reaction. CARANAMINES Only one caranamine was known, when we commenced our work (137), namely a dextrorotatory caran-4-amine (138). However during the course of the work a preparation of (+)-trans-caran-cis-2-amine, presumably Baeyer's amine (138), was described (139). We have therefore worked out (137) stereospecific routes to the following: (--)-trans-caran-cis-2-amine (for-. mula 49) (the enantiomorph of Baeyer's amine), (--)-cis-caran-trans-2- amine (formula 50), (+)-cis-caran-cis-4-amine (formula 51), (--)-cis-caran-

268 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS H2N• • NH2 (490) [(49) (50) • N H2H2N•____ (5/) (51o) ( 5lb ) NH2 ' I (54) NH2 (540) N• trans-4-amine (formula 52), (+)-cis-caran-cis-5-amine (formula 53) and (--)-cis-caran-tran,-5-amine (formula 54). With suitable elaboration these .amines might give compounds of useful physiological properties. They are in fact strong bases which rapidly form carbonates with atmospheric carbon dioxide.