Hodgson David M, Le Strat Frédéric, Avery Thomas D, Donohue Andrew C, Brückl Tobias
Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, United Kingdom.
J Org Chem. 2004 Dec 10;69(25):8796-803. doi: 10.1021/jo048446b.
Levulinic acid-derived 6-diazoheptane-2,5-dione (9) serves as a common precursor in a formal synthesis of frontalin 19, and in syntheses of cis-nemorensic acid 1, 4-hydroxy-cis-nemorensic acid 2, 3-hydroxy-cis-nemorensic acid 3, and nemorensic acid 4. The key step in these syntheses is the Rh(2)(OAc)(4)-catalyzed tandem carbonyl ylide formation-intermolecular 1,3-dipolar cycloadditions of diazodione 9 with formaldehyde, alkynes or allene, which occur with high regioselectivity. Subsequent oxidative cleavage of the ring originally derived from the cyclic carbonyl ylide intermediate provides a straightforward access to polysubstituted tetrahydrofurans, and in particular an efficient entry to the nemorensic acids. Enantioselective cycloadditions with diazodione 9, using chiral rhodium catalysts, gave cycloadducts in up to 51% ee.
源自乙酰丙酸的6-重氮庚烷-2,5-二酮（9）是在frontalin 19的形式合成以及顺式-降香酸1、4-羟基-顺式-降香酸2、3-羟基-顺式-降香酸3和降香酸4的合成中的常见前体。这些合成中的关键步骤是Rh(2)(OAc)(4)催化的重氮二酮9与甲醛、炔烃或丙二烯的串联羰基叶立德形成-分子间1,3-偶极环加成反应，该反应具有高区域选择性。随后对最初源自环状羰基叶立德中间体的环进行氧化裂解，提供了一条直接通向多取代四氢呋喃的途径，特别是一种高效合成降香酸的方法。使用手性铑催化剂与重氮二酮9进行对映选择性环加成反应，得到的环加成产物的对映体过量率高达51%。
