A very short reaction sequence opens with metal-mediated 
 addition of commercial bromodifluoropropene to aldehydes; allylation under 
 phase transfer catalysed conditions sets the stage for a ring closing 
 metathesis (RCM) in the presence of commercial Grubbs’ catalyst to 
 afford potentially useful difluorinated dihydropyrans.
                                    在极短的反应序列中,首先是以
金属为介质将商用
溴二
氟丙烯加到醛中,然后在相转移催化条件下进行烯丙基化反应,最后在商用格拉布斯催化剂的作用下进行闭环偏聚反应(RCM),得到可能有用的二
氟化二氢
吡喃。