Formation of Titanium-Metallacycles and Exploration of Their Reactivities

1.在二茂钛（II）催化下，（Z）-烯基砜与羰基化合物通过氧杂环戊烷反应得到（E）-烯丙醇。（Z）-烯基砜与炔的类似反应通过形成钛环戊烯立体选择性地产生共轭二烯而进行。当使用乙炔基羧酸衍生物和烯酰基膦酸酯时，还获得二烯羧酸、二烯羧酸酯和二烯基膦酸酯。用（Z）-烯基砜-二茂钛（II）体系对炔基砜进行烯基化反应，然后将所得的α-磺酰基烯基钛化合物进行还原钛化反应，得到钛-乙烯基亚乙烯基络合物，该络合物与羰基化合物反应，得到具有完全E-选择性的烯基联烯.合成了具有不同取代模式的钛环丁烯，并考察了它们对酮和末端烯烃的反应活性。发现钛环丁烯类化合物存在于反应体系中， 关于我们 与钛-烯基卡宾络合物的平衡和平衡的位置取决于它们的取代模式。维蒂希型烯化产物亚烷基环丙烷是通过包括羧酸衍生物在内的羰基化合物与钛-亚环丙烷配合物反应获得的，钛-亚环丙烷配合物是通过1，1-二氯环丙烷与二茂钛（II）试剂的还原钛化反应产生的。多种多卡宾络合物，有机钛物种具有多个钛-卡宾络合物的子结构，也通过多硫代缩醛的脱硫钛化制备。这些物种与羰基化合物反应生成各种高度共轭的化合物。烯丙基钛物种是通过钛-烷叉络合物与炔基砜反应生成的钛环丁烯的β-消除而产生的。这些有机钛物种与酮的处理，得到顺叔高炔丙醇具有高的非对映选择性。与此相反，钛-环亚丙基配合物与炔反应生成的具有螺键合的环丙烷的钛环丁烯被发现是热稳定的，并且可以被分离。这些钛环水解生成烯基环丙烷，阐明了四元和五元钛环反应活性的结构依赖性，从而为有机钛化学开辟了新的领域。少

1. (E)-Allylic alcohols were obtained via oxatitanacyclopentanes by the titanocene(II)-promoted reaction of (Z)-alkenyl sulfones with carbonyl compounds. The similar reactions of (Z)-alkenyl sulfones with alkynes proceeded via the formation of titanacyclopentenes to produce conjugated dienes stereoselectively. Dienecarboxylic acids, dienecarboxylic esters, and dienylphosphnic esters were also obtained when acetylenecarboxylic acid derivatives and alynylphosphonic esters were employed. The alkenylation of alkynyl sulfones with the (Z)-alkenyl sulfones-titanocene(II) system and the following reductive titanation of the resulting α-sulfonylalkenyltitaniurn compounds produced titanium-vinylvinylidene complexes which gave alkenylallenes with complete E-selectivity on treatment with carbonyl compounds.2. Titancyclobutenes with various substitution patterns were synthesized and their reactivity toward ketones and terminal alkenes was examined. It was found that titanacyclobutenes exist in equ … More ilibrium with titanium-alkenylcarbene complexes and the position of equilibrium depends on their substitution patterns.3. The Wittig-type olefination products, alkylidenecyclorpropanes, were obtained by the reaction of carbonyl compounds including carboxylic acid derivatives with titanium-cyclopropylidene complexes generated by the reductive titanation of 1,1-dichlorocyclopropanes with the titanocene(II) reagent. A variety of multicarbene complexes, organotitanium species having a plurality of titanium-carbene complex substructures, were also prepared by the desulfurizative titanation of multithioacetals. These species reacted with carbonyl compounds to produce various highly conjugated compounds.4. Allenyltitanium species were produced by the β-elimination of the titanacyclobutenes generated by the reaction of titanium-alkylidene complexes with alkynyl sulfones. The treatment of these organotitanium species with ketones gave syn-tertiary homopropargyl alcohols with high diastereoselectivity. In contrast, the titanacyclobutenes with a spiro-bonded cyclopropane generated by the reaction of titanium-cyclopropylidene complexes with alkynes were found to be thermally stable and could be isolated. The hydrolysis of these titanacycles produced alkenylcyclopropanes.The structure-dependence of reactivity of four- and five-membered titanacycles was elucidated by the present study, and thus a new field of organotitanium chemistry will be opened. Less