Tandem Cycloaddition Chemistry of 2-Azoniaheterodienes

描述（由申请人提供）：本申请的基本目的是开发和应用两个2-氮杂二烯（硝基烯烃和N-乙烯基硝酮基团）的串联[4+2]/[3+2]环加成反应。该计划分为两个主要部分，具有不同的具体目标，但统一在天然和非天然杂环化合物制备的新反应化学的共同主题中。 与硝基烯烃有关的方法学目标分为两部分。第一个将涉及扩展已建立的硝基烯烃的环加成化学，以通过以下方式获得不同大小的环：（1）亲二烯体变化（1-和2-烷氧基二烯），（2）使用手性刘易斯酸催化[4+2]过程和（3）和研究改性的亲偶极体，以在[3+2]环加成后并入较大的环。方法学研究的第二部分是对内/内[4+2]/[3+2]串联环加成反应的探索和发展。这个新的家庭的转换将允许快速和选择性的建设复杂的多环系统从简单的无环前体。一个主要的活动将是评估范围，可行性和立体控制元素在选定的排列这一类。 串联硝基烯烃环加成的合成目标包括许多生物碱家族中的天然化合物。选择Scandine（一种Melodinus生物碱）UCS 1025 A/B（一种罕见的吡咯里西啶生物碱）和Daphnilactone（一种虎皮楠生物碱）来突出不同串联过程的战略力量。有趣的新一类1-氮杂菲烷也将被准备用于评估中心碳的扭曲。 该提案的第二个主要部分是N-乙烯基硝酮的环加成化学的发明、发展和探索，这是一个新的2-azoniaheterodienes家族。这些杂化杂二烯/偶极为哌啶和哌啶嵌入的多环化合物的一般合成提供了巨大的潜力。制备，结构，稳定性，反应性（在[4+2]和[3+2]流形）的基本特征将得到解决，特别注意串联环加成与分子内拴系组件的机会。

DESCRIPTION (provided by applicant): The basic objectives of this application are the development and application of the tandem [4+2]/[3+2] cycloaddition reactions of two 2-azoniaheterodienes, the nitroalkene and N-vinylnitrone groups. The program is divided into two major sections with different specific aims but unified in the common theme of new reaction chemistry for the preparation of natural and non-natural heterocyclic compounds. The methodological objective relating to nitroalkenes is subdivided into two parts. The first will involve the expansion of the established cycloaddition chemistry of nitroalkenes to access different size rings through: (1) dienophile variation (1- and 2-alkoxydienes), (2) the use of chiral Lewis acid catalysis the [4+2] process and (3) and investigation of modified dipolarophiles to incorporate larger rings after [3+2] cycloaddition. The second part of the methodological study is the exploration and development of the intra/intra [4+2]/[3+2] tandem cycloadditions. This new family of transformations will allow for the rapid and selective construction of complex polycyclic ring systems from simple acyclic precursors. A major activity will be the assessment of scope, viability and stereocontrol elements in selected permutations of this class. Synthetic targets for the tandem nitroalkene cycloaddition include natural compounds in a number of alkaloid families. Scandine (a melodinus alkaloid) UCS1025A/B (a rare pyrrolizidine alkaloid) and daphnilactone (a daphniphyllum alkaloid) are chosen to highlight the strategic power of different tandem processes. The intriguing new class of 1-azafenestranes will also be prepared to assess the distortion of the central carbon. The second major section of the proposal is the invention, development and exploration of the cycloaddition chemistry of N-vinylnitrones, a new family of 2-azoniaheterodienes. These hybrid heterodiene/dipoles offer great potential for the general synthesis of piperidines and piperidine-embedded polycyclic compounds. The basic features of preparation, structure, stability, reactivity (in both [4+2] and [3+2] manifolds) will be addressed with particular attention to opportunities in tandem cycloadditions with intramolecularly tethered components.