Tuesday 16 September 2014

Multi-step synthesis using modular flow reactors: the preparation of yne-ones and their use in heterocycle synthesis



Multi-step synthesis using modular flow reactors: the preparation of yne-ones and their use in heterocycle synthesis 

I.R. Baxendale, S.C. Schou, J. Sedelmeier, S.V. Ley, Chem. Eur. J. 2010, 16, 89-94.

 http://onlinelibrary.wiley.com/doi/10.1002/chem.200902906/abstract

 Thumbnail image of graphical abstract






Multi-step in flow: The palladium-catalysed acylation of terminal alkynes for the synthesis of yne[BOND]ones as well as their further transformation to various heterocycles in a continuous-flow mode is presented. Furthermore, an extension of the simple flow configuration that allows for easy batch splitting and the generation of a heterocyclic library is described (see scheme).

Wednesday 10 September 2014

CH2 Adds Something to Fullerenes



CH2 Adds Something to Fullerenes

Methylene addends in fullerene electron acceptors increase solar-cell efficiency
Read more



 Fullerene derivatives are used as electron acceptors in organic solar cells. CH2 addends can effectively raise fullerene lowest unoccupied molecular orbital (LUMO) energy levels, which leads to high open-circuit voltage (Voc). As the smallest addend, CH2 does not affect fullerene packing in the solid state, thus keeping good electron mobility for the acceptors.


 http://www.chemistryviews.org/details/ezine/6508231/CH2_Adds_Something_to_Fullerenes.html

Carbohydrate Orientation



 thumbnail image: Carbohydrate Orientation

 

Carbohydrate Orientation

Incorporation of a photosensitive azobenzene linker for controllable carbohydrate orientation
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 Carbohydrate recognition is an important biological process that is essential for the communication between cells, such as cellular adhesion and recognition. A control of the spatial orientation of these carbohydrate units could potentially be used to modify this recognition event.

 http://www.chemistryviews.org/details/ezine/6533751/Carbohydrate_Orientation.html

Remold Crystals with Vapor



Remold Crystals with Vapor

Halogen bonding drives the conversion from surface-confined crystals to co-crystals without the use of solvent
Read more



 The ultimate application of functional materials requires successful fabrication of devices. For organic molecules, this usually involves the deposition of organic thin films on surfaces, which often limits the options for subsequent modification and optimization.


 http://www.chemistryviews.org/details/news/6543561/Remold_Crystals_with_Vapor.html

Monday 8 September 2014

Mechanism for pyrrole synthesis




This shows the tradtional mechanism for forming a pyrrole ring using a 1,4-diketone and ammonia. The hydroxyl groups are removed as water in two separate dehydration steps, forming enamines in two of the intermediates.
A new mechanism, which does not require enamine formation, has been proposed based on a study using Density Functional Theory.


This shows the mechanism for pyrrole synthesis based on recent DFT study. Instead of the formation and cyclisation of a enamine intermediate, a hemiaminal intermediate in formed, followed by the consecutive dehydrations of the two hydroxyl groups. The dehydration steps may look familiar: it is just the formation of an enamine






A more traditional approach to the mechanism, which appears in some text books and taught courses, can be found here.

 Sn2
 
This mechanism was based on the paper: B. Mothana, R. J. Boyd, J. Mol. Struct.: THEOCHEM, 2007, 811, 97-107

Saturday 6 September 2014

Synthesis of 2-dimethylaminomethyl-cyclohexanone hydrochloride

Synthesis of 2-dimethylaminomethyl-cyclohexanone hydrochloride

http://orgspectroscopyint.blogspot.in/2014/09/synthesis-of-2-dimethylaminomethyl.html




Cyclohexanone+Paraformaldehyde+Dimethylammonium chloride
EtOH, HCl
reacts to
2-Dimethylaminomethyl cyclohexanone hydrochloride

Synthesis of 2-dimethylaminomethyl-cyclohexanone hydrochloride

Reaction type:reaction of the carbonyl group in aldehydes, Mannich reaction
Substance classes:ketone, aldehyde, amine
Techniques:heating under reflux, stirring with magnetic stir bar, evaporating with rotary evaporator, filtering, recrystallizing, heating with oil bath
Degree of difficulty:Easy


Equipment


round bottom flask 25 mLround bottom flask 25 mLreflux condenserreflux condenser
suction filtersuction filtersuction flasksuction flask
heatable magnetic stirrer with magnetic stir barheatable magnetic stirrer with magnetic stir barrotary evaporatorrotary evaporator
exsiccator with drying agentexsiccator with drying agentoil bathoil bath


Operating scheme



Inline image 1


Instruction (batch scale 100 mmol) 
Equipment 
100 mL round bottom flask, reflux condenser, Buechner funnel (Ø 5.5 cm), suction flask, 
heatable magnetic stirrer, magnetic stir bar, rotary evaporator, desiccator, oil bath 
Substances 
cyclohexanone (bp 156 °C) 9.82 g (10.3 mL, 100 mmol) 
paraformaldehyde (mp 120-170 °C) 3.60 g (120 mmol) 
dimethylammonium chloride 8.16 g (100 mmol) 
hydrochloric acid (conc.) 0.4 mL 
ethanol (bp 78 °C) 64 mL 
acetone (bp 56 °C) 180 mL 

Reaction 
9.82 g (10.3 mL, 100 mmol) cyclohexanone, 3.60 g (120 mmol) paraformaldehyde, 8.16 g 
(100 mmol) dimethylammonium chloride and 4 mL ethanol are filled in a 100 mL round 
bottom flask with reflux condenser and magnetic stir bar. 0.4 mL conc. hydrochloric acid are 
added and the mixture is heated under stirring for 4 hours under reflux. 
Work up 
The hot solution is filtered in a round-bottom flask and the solvent is evaporated at the rotary 
evaporator. The residue is dissolved in 20 mL ethanol under heating. At room temperature 
70 mL acetone are added to the solution. For complete crystallization the solution is stored 
over night in the freezer compartment. The crystallized crude product is sucked off over a 
Buechner funnel (Ø = 5.5 cm) and dried in the desiccator over silica gel. 
Crude yield: 15.6 g; mp 149-150 °C 
For further purification the crude product is again dissolved in about 40 mL ethanol under 
reflux and at room temperature 110 mL acetone are added. The crystallization is completed in 
the freezer compartment. The product is sucked off and dried in the desiccator. 
Yield: 14.7 g (76.7 mmol, 77%,); mp 156-157 °C 
Comments 
To verify a complete crystallization, the mother liquor is stored in the freezer compartment. 
No product should crystallize any further.





Simple evaluation indices


Atom economynot defined
Yield76%
Target product mass1.45g
Sum of input masses54g
Mass efficiency27mg/g
Mass index37g input / g product
E factor36g waste / g product





1H NMR

Inline image 2


Inline image 3


1H-NMR: 2-Dimethylaminomethyl cyclohexanone hydrochloride
500 MHz, CDCl3
delta [ppm]mult.atomsassignment
1.35m1 H
1.54m1 H
1.73m1 H
1.82m1 H
2.05m1 H
2.37m2 H6-H (ring)
2.41m1 H
2.67d3 HN-CH3
2.74m1 H
2.77d3 HN-CH3
3.09m1 HN-CH2
3.57m1 HN-CH2
11.88m1 HN-H
7.26CHCl3
13C NMR


Inline image 4
Inline image 5

13C-NMR: 2-Dimethylaminomethyl cyclohexanone hydrochloride
125 MHz, CDCl3
delta [ppm]assignment
24.70C5
27.70C3
33.88C4
41.75CH3
42.26CH3
44.99C6
46.69C2
56.80-CH2-N-
209.58C1 (C=O)
76.5-77.5CDCl3

IR


Inline image 6

IR: 2-Dimethylaminomethyl cyclohexanone hydrochloride
[Film, T%, cm-1]
[cm-1]assignment
3068, 3020N-H valence
2932, 2858C-H valence
1698C=O valence, ketone