Synthesis of Novel Oxime Functionalized Aldol Products via Michael Addition of Oximes Onto Baylis–Hillman Adducts
摘要:
Triphenylphosphine-catalyzed Michael addition of oximes 2 onto Baylis-Hillman (B-H) adducts 1 led to an easy access to a novel class of oxime functionalized aldol products 3. This demonstrates the first use of an oxygen-centered nucleophile in Michael addition to B-H adducts, without touching any other functional group. Deprotection of oxime in 3 was further demonstrated using molecular hydrogen (1 atm) and 10% Pd/C (cat.) to furnish functionalized 1,3-diols 4 as potentially useful synthons with optional backbone choice (R 3 and EWG).
The coupling of α,β-unsaturated carbonyl compounds with aldehydes (the Baylis-Hillman reaction) was accelerated in the presence of a catalytic amount of 1,4-diazabicyclo[2,2,2]octane (DABCO) and lithium perchlorate in ether. A preliminary kinetic study revealed that the relative rate of the reaction using LiClO4 in ether was 8.0×102 times faster than that of the reaction without LiClO4.
Catalyst-Free Synthesis of Skipped Dienes from Phosphorus Ylides, Allylic Carbonates, and Aldehydes via a One-Pot S<sub>N</sub>2′ Allylation–Wittig Strategy
A catalyst-free allylic alkylation of stabilized phosphorus ylides with allylic carbonates via a regioselective SN2′ process is presented. Subsequent one-pot Wittig reaction with both aliphatic and aromatic aldehydes as well as ketenes provides structurally diverse skipped dienes (1,4-dienes) in generally high yields and moderate to excellent stereoselectivity with flexible substituent patterns. This
提出了通过区域选择性的S N 2'方法将稳定的磷化磷与烯丙基碳酸酯进行无催化剂的烯丙基烷基化反应。随后的与脂肪族和芳香族醛以及乙烯酮的一锅Wittig反应可提供结构多样的跳跃式二烯(1,4-二烯),且产率高,并且具有灵活的取代基图案,具有中等至出色的立体选择性。这种单锅S N 2'烯丙基化-维蒂希(Wittig)策略构成了一种方便有效的合成方法,用于从容易获得的起始原料中高度官能化的二烯。
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‐Dichlorocyclopropanation of Dicarbonyl Derivatives
作者:Gabriel M. F. Batista、Pedro P. De Castro、Arthur G. Carpanez、Bruno A. C. Horta、Giovanni W. Amarante
DOI:10.1002/chem.201904149
日期:2019.12.20
A novel methodology for the 1,1‐dichlorocyclopropanation of dicarbonyl conjugated olefins was described. The developed protocol is simple and uses readily accessible starting materials, allowing the isolation of the desired adducts in moderate to excellent yields (up to 99 %). Furthermore, the reaction tolerated scale up to the gram scale; thus highlighting the synthetic potential of this transformation
Porcine Liver Esterase Catalyzed Kinetic Resolution of Baylis-Hillman (B-H) Adducts
作者:Debnath Bhuniya、Sanju Narayanan、Taranpreet Singh Lamba、K. V. S. R. Krishna Reddy
DOI:10.1081/scc-120025180
日期:2003.11
Esterase from porcine liver smoothly resolves varieties of racemic 2-methylene-3-substituted-3-hydroxypropanoates (B-H adducts) to obtain the corresponding unreacted esters in very good to excellent ee (94 to >99%, seven examples) and hydrolyzed acids in good ee (58-75%). Substitution in B-H adducts, chosen for resolution, are funtionalized phenyl, thiophen-3-yl, cinnamyl, and alkyl groups.