Namboothiri Irishi N N, Ganesh Madhu, Mobin Shaikh M, Cojocaru Miriam
Department of Chemistry and National Single-Crystal X-ray Diffraction Facility, Indian Institute of Technology, Bombay, Mumbai 400 076, India.
J Org Chem. 2005 Mar 18;70(6):2235-43. doi: 10.1021/jo048262x.
[reaction: see text] A variety of key precursors to the intramolecular Diels-Alder reaction of furan diene (IMDAF) have been prepared via a very facile 1,4-addition of O-, S-, N-, and C-centered nucleophiles possessing unsaturated tether to beta-furyl nitroethylene. Subsequent IMDAF reaction of the 1,4-adducts, carried out under thermal conditions, provided five- and six-membered carbocycles and heterocycles fused to an easily cleavable oxabicycloheptene moiety. The structure and stereochemistry of the cycloadducts were determined by 2D-NMR experiments and further confirmed by X-ray crystallography. The salient features of the strategy include high degree of stereoselectivity (>80:20) in the cycloaddition, atom and step economy, and generation of multiple chiral centers and functionalities. The feasibility of the cleavage of the oxa bridge in the cycloadducts to afford novel multifunctional molecules has also been demonstrated.
[反应：见正文] 通过具有不饱和连接基的O-、S-、N-和C-中心亲核试剂与β-呋喃基硝基乙烯进行非常简便的1,4-加成反应，制备了多种用于呋喃二烯分子内Diels-Alder反应（IMDAF）的关键前体。随后在热条件下对1,4-加成产物进行IMDAF反应，得到了与易于裂解的氧杂双环庚烯部分稠合的五元及六元碳环和杂环。通过二维核磁共振实验确定了环加成产物的结构和立体化学，并通过X射线晶体学进一步证实。该策略的显著特点包括环加成反应中高度的立体选择性（>80:20）、原子经济性和步骤经济性，以及生成多个手性中心和官能团。还证明了环加成产物中氧杂桥裂解以提供新型多功能分子的可行性。
