Sequence [2,3]-Sigmatropic Rearrangement: One-Pot Synthesis of Proparggyl Allenylamines

Allenes,served as highly sought-after building blocks,are an indispensable component of synthetic chemistry.Their utility in modulating the chemical,physical,and pharmaceutical properties of organic compounds make allenes a desirable choice in various applications.Here,we report a facile method for the atom-economical synthesis of propargyl allenylamines via an underdeveloped[2,3]-sigmatropic rearrangement.Our strategy employs easily accessible propargylamines as starting materials,which are first converted into propargyl ammonium salts,followed by a base-promoted[2,3]-sigmatropic rearrangement.This one-pot,two-step reaction proceeds in the absence of transition metals,displays a very broad scope,and does not require the introduction of the electron-withdrawing group into the starting materials.

Sigmatropic rearrangements of B(MIDA)-propargylic alcohols towards the diverse synthesis of α-functionalized organoborons

α-Functionalized organoborons are useful building blocks and key structural elements in functional molecules.Their previous synthesis relied on the famous Matteson reaction or the late-stage borylative modification of alkynes or alkenes.Recently,the synthetic transformation of borylated building blocks offers another useful strategy and is currently actively explored.We report herein that B(MIDA)-propargylic alcohols(BPAs) are a useful type of borylated building blocks.Bearing two complementary functional group handles(alkyne and hydroxyl) in close proximity,the redox-neutral [3,3] and [2,3] sigmatropic rearrangements of BPAs allow the efficient synthesis of several types of α-functionalized boronates,including α,β-unsaturated acylborons,α-S/P-substituted allenylborons,boryl-substituted thiazoles and a borylated α,β-unsaturated hydrazine,some of which are otherwise challenging targets using other synthetic methods.

Catalyst-Free Imidation of Allyl Sulfides with Chloramine-T and Subsequent [2,3]-Sigmatropic Rearrangement

A facile synthesis of various allyl sulfonamides based on imidation of allyl sulfides with chloramine-T and sub- sequent [2,3]-sigmatropic rearrangement has been achieved without metal catalysts. The reaction completes smoothly within 10 min, providing excellent yields in environment friendly solvent of alcohol. Functional groups such as bromine, hydroxyl, protected amido and aldehyde are tolerant under this condition.

The Wittig sigmatropic rearrangement in a conjugated diene system Ⅰ

A conjugated dienic benzyl ether was shown to undergo Wittig sigmatropic rearrangement to give a mixture of[1,2]and[1,4]besides the expected[2,3]rearrangement product.The solvent effect as well as the reaction pathways were discussed.

The Mechanism on Cyclization, Debenzylation and Oxidation of 1-[1-(Benzyloxy)-3-methylnaphthalen-4-yloxy]propan-2-one

1-[1-（Benzyloxy）-3-methylnaphthalen-4-yloxy]propan-2-one （la） took place a cyclization, debenzylation and oxidation to form 9-substitued benzo[de]chromene-7,8-dione （2a） and 5-benzyl-9-substitued benzo[de]chromene-7,8-dione （3a）. The mechanisms for these reactions were discussed.

Photochemical Transformations of Some 2-（5-Methylthiophen-2-yl）-3-[（naphthalen-2-yl）methoxy]-4H-chromen-4-ones Involving Type-II Process

Photo-irradiation of 2-（5-methylthiophen-2-yl）-3-[（naphthalen-2-yl）methoxy]-4H-chromen-4-ones yielded the fascinating angular tetracyclic products via cyclization involving both 2-thienyl ring and naphthylmethoxy group via 1,4-biradical generated in the Norrish type-II process. The stereochemical dispositions of the products were determined by MM2 energy minimized programme and spectroscopic analysis.