| 摘要 |
Title cpds of formula (I) are prepared by cyclisation of (II) using 90-98% (pref. 96-98%) H2SO4 at -30 to +20 degrees C in the presence of opt. chlorinted liquid hydrocarbons (bp 200 degrees C) and low m.wt. aliphatic alcohols. - The molar ratio of II alcohol is 1:0.5-5 (pref. 0.5-2) the molar ratio of II H2SO4 is 1:5-15 (pref. 7-12). - The volume ratio of II hydrocarbon is pref. 1:1-17 (esp. 2-14). - The product is free from alpha-ionones and may be used directly in the vitamin A synthesis (where R1,R2,R3=H, nethl X=R1-CH-C(CH3)=CH2, R1-C=C(CH3)2, R1=CH-C(CH3)2-OCH3 Y= -C(CH3)=CH).
|
