Development of Allyl-Transfer Reaction and Its New Aspect

迄今为止，还没有报道通过醛的烷-2-烯化（RCHO）有效合成高烯丙醇（2，RCH（OH）CH_2CH=CHR^3）的方法。另一方面，我们最近发现了第一个方便的和高度立体选择性的醛的丁-2-烯基化（RCHO），（RC^*H（OH）CH_2CH=CHCH_3），其中高烯丙醇的γ-加合物（一、R^1R^2C^*（OH）C^*HR^3CH=CH_2）作为烯丙基给体存在，其烯丙基官能团（R^3CH=CHCH_2）通过氧代碳正离子中间体的最稳定的六元椅式环状过渡态发生[3.3]-σ迁移重排，转化为醛（RCH=O^+C^*R^1R^2C^*HR^3CH=CH_2; R^3=CH_3）衍生自醛的半缩醛（RCH（OH）OC^*R^1R^2C^*HR^3CH=CH^2）和1.此外，我们证明了醛的烷-2-烯基化的可能性，通过烯丙基转移反应使用光学活性的薄荷酮（（-）-，（+）-，（+）-异）作为手性助剂。我们还发现，由于烷基链的空间位阻增加，这提高了产物的产率。通过2与醛的Prins环化反应，高产率地合成了高光学活性的2，3，4，6-四取代四氢吡喃，最近我们发现了醛的不对称4-苄氧基丁-2-烯化反应，得到高烯丙醇的α-加成物（RC^*H（OH）CH_2CH=CHCH_2OBn），成功地合成了所需的高烯丙醇（R^4C^*H（HO）C^*HR^3CH=CH^2; R^3=CH_2OBn）而不使用有机金属化合物如R^3CH=CHCH_2M（M=金属），由于其不稳定性，（当R^3=CYR_2;Y=OBn，卤素时）.我们发现了“烯丙基转移反应”，它能方便地得到高烯丙醇的高光学活性和多种功能化的α-加成物.

To date, there have been no reported methods for effectively synthesizing homoallylic alcohols (2,RCH(OH)CH_2CH=CHR^3) via alk-2-enylation of aldehydes (RCHO). On the other hand, we recently discovered the first convenient and highly stereoselective but-2-enylation of aldehydes (RCHO) to give (RC^*H(OH)CH_2CH=CHCH_3) by allyl-transfer reaction, in which γ-adduct of homoallylic alcohol (1,R^1R^2C^*(OH)C^*HR^3CH=CH_2) surved as an allyl donor and its allylic functionality (R^3CH=CHCH_2) was transfered to aldehyde due to [3.3]-sigmatropic rearrangement via the most stable 6-membered chair-like cyclic transition state of the oxocarbenium ion intermediate (RCH=O^+C^*R^1R^2C^*HR^3CH=CH_2; R^3=CH_3) derived from hemiacetal (RCH(OH)OC^*R^1R^2C^*HR^3CH=CH^2) of aldehyde and 1. Further, we demontrated the possibility of alk-2-enylation of aldehydes via an allyl-transfer reaction using optically active menthones ((-)-,(+)-, and (+)-iso) as chiral auxiliaries. We also discovered that this improved the yield of the product due to an icrease in the steric valk of the alkyl chains. Highly optically acitive 2,3,4,6-tetrasubstituted tetrahydropyrans were prepared in good yield by Prins cyclization reaction of 2 and aldehydes.More recently, we discovered an asymmetric 4-benzyloxybut-2-enylation of aldehydes to give α-adduct of homoallylic alcohols (RC^*H(OH)CH_2CH=CHCH_2OBn), in which we successfully prepared the necessary homoallylic alcohol (R^4C^*H(HO)C^*HR^3CH=CH^2; R^3=CH_2OBn) without using organometallic compounds such as R^3CH=CHCH_2M (M=metal) which is impossible to prepare because of its intability (when R^3=CYR_2;Y=OBn, halogens).We discovered "Allyl-Transfer reaction" which gave highly optically active and a variety of fuctionalyzed α-adduct of homoallylic alcohols, conveniently.