When a phenol having substituents in at least the 2- and 4-positions but having a hydrogen atom in the 6-position, or a phenol having substituents in at least the 2- and 6-positions but having a hydrogen atom in the 4-position is reacted with formaldehyde and 1,3-propanediamine, a unique insertion-condensation reaction occurs whereby the product is a hexahydropyrimidine derivative which may be represented by the general formula
 wherein R₁ is (i) a 2-hydroxybenzyl group having an inert substituent (preferably a hydrocarbyl substituent) in at least the 3- and 5-positions or (ii) a 4-hydroxybenzyl group having an inert substituent (preferably a hydrocarbyl substituent) in at least the 3- and 5-positions; and R₂ is (i) a 2-hydroxybenzyl group having an inert substituent (preferably a hydrocarbyl substituent) in at least the 3- and 5-positions or (ii) a 4-hydroxybenzyl roup having an inert substituent (preferably a hydrocarbyl substituent) in at least the 3- and 5-positions or (iii) a hydrogen atom. Uses for such compounds   include their use as antioxidants and stabilizers for various substrates, such as fuels, lubricants, and functional fluids.  
                            当至少在 2-位和 4-位上有取代基但在 6-位上有氢原子的
苯酚,或至少在 2-位和 6-位上有取代基但在 4-位上有氢原子的
苯酚与
甲醛和 
1,3-丙二胺反应时,会发生独特的插入-缩合反应,生成物是六氢
嘧啶衍
生物,其通式为
 其中 R₁ 是 (i) 至少在 3 和 5 位上具有惰性取代基(最好是烃基取代基)的 2-羟基苄基,或 (ii) 至少在 3 和 5 位上具有惰性取代基(最好是烃基取代基)的 
4-羟基苄基;R₂是(i)至少在 3 和 5 位上具有惰性取代基(最好是烃基取代基)的 2-羟基苄基,或(ii)至少在 3 和 5 位上具有惰性取代基(最好是烃基取代基)的 
4-羟基苄基,或(iii)氢原子。此类化合物的用途包括用作各种基质(如燃料、润滑剂和功能性液体)的
抗氧化剂和稳定剂。