Regio- and diastereoselective synthesis of diverse spirocyclic indenes by cyclization with indene-dienes as two carbon building blocks

We report a base-promoted cyclization with indene-dienes as two carbon building blocks toward diverse spirocyclic indene scaffolds including hexacyclic spiroindenes bearing benzo pyran motifs and pentacyclic spiroindenes containing oxindole units in high yields with excellent diastereoselectivities.

Difluorodiazoethane as a masked acetylene equivalent in formal [3 + 2] cycloadditions with ketones to access 2,3-functionalized furans

A transition-metal-free [3+2] cycloaddition of CF2HCHN2 with β-ketones is reported, which enables the synthesis of 2,3-functionalized furans. Sequential defluorination, nucleophilic addition, and cyclization are key elemental steps of the reaction.

Unveiling the [3+2] cycloaddition between difluoromethyl diazomethane and 3-ylideneoxindole from the perspective of molecular electron density theory

Evolution of some key ELF basins along the IRC of the most favorable ortho/endo reaction path.

Ex Situ Generation of Difluorodiazoethane (CF2HCHN2): Application in the Regioselective Synthesis of CF2H-Containing Pyrazoles

A new method for the ex situ generation of difluorodiazoethane (CF₂HCHN₂) and a procedure for its efficient use in [3 + 2] cycloaddition with nitroolefins by the AcOH/O₂ catalyst system were developed by using a simple two-chamber system. The method provides a facile and straightforward access to a series of 4-substituted 5-difluoromethyl-3-nitro-1H-pyrazoles that are of interest in medicinal chemistry. Interestingly, the key factor for the success of this method is the efficient preparation of CF₂HCHN₂ by an ex situ process.

Synthesis and crystal structure of (±)-Ethyl 5′-(difluoromethyl)-2-oxo-4′,5′-dihydrospiro[indoline-3,3′-pyrazole]-4′-carboxylate, C14H13F2N3O3

C14H13F2N3O3, triclinic, P1̄ (no. 2), a = 9.4486(7) Å, b = 12.4694(8) Å, c = 13.8690(8) Å, α = 65.734(6)°, β = 74.523(5)°, γ = 83.726(6)°, V = 1435.63(18) Å3, Z = 4, Rgt (F) = 0.0495, wR ref(F 2) = 0.1249, T = 293(2) K.

Regio- and stereoselective [3 + 2] cycloaddition reaction: access to isoxazole-dispirobisoxindoles featuring three contiguous stereocenters

A novel methodology toward the diversity-oriented asymmetric construction of densely functionalized isoxazole-dispirobisoxindoles was developed.

19F-NMR Diastereotopic Signals in Two N-CHF₂ Derivatives of (4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-2H-indazole

In this paper, we report the anisochrony of the fluorine atoms of a CHF₂ group when linked to a pyrazole ring. The pyrazole is part of (4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-4,7-methano-2H-indazole also known as (4S,7R)-campho[2,3-c]pyrazole, which has two stereogenic centers. Gauge-Independent Atomic Orbital (GIAO)/Becke, 3-parameter, Lee-Yang-Parr (B3LYP)/6-311++G(d,f) calculated 19F chemical shifts of the minimum energy conformations satisfactorily agree with the experimental data. The energy differences between minima need to consider solvent effects (continuum model) to be satisfactorily reproduced.