Cabocation NMR

The carbocations (2) and (3) only differ in the positions of electrons, so they are resonance forms of the same ion, and can be described as a non-classical carbocation. NMR evidence for the non-classical nature of such cations is given in March (6th ed.), pp. 1582–1583.

Wagner-Meerwein shift

Camphene hydrochloride–isobornyl chloride rearrangment

J. Org. Chem. (1999) 64, 60–64

In the presence of a Lewis acid catalyst, camphene hydrochloride (1) rearranges to isobornyl chloride (2).



The mechanism is believed to involve the following steps:

• the Lewis acid catalyst abstracts chloride from camphene hydrochloride (1), leaving behind a tertiary carbocation (2)
• the tertiary carbocation (2) rearranges to a secondary carbocation (3) by a [1,2]-alkyl shift
• a chloride ion adds to the secondary carbocation (3), forming isoborny chloride (4)

The OH of 3-cyclohexenol can be removed using superacid:

The NMR of the cation can be recorded, at -80°:

The central 141.9 ppm carbon is typical of a double bond.

The 224.4 ppms are highly deshielded, but not as much as a localized carbocation, which would be around 330 ppm:

Anti-cyclooctadiene derivative 15: 


1H NMR (600 MHz, CDCl3) δ 6.45 (dd, 2H, J1 = 1.84, J2 = 7.80 Hz), 6.41 (d, 2H, J = 1.84 Hz), 6.31 (d, 2H, J = 7.80 Hz), 6.05–6.00 (m, 2H), 5.94–5.88 (m, 2H), 4.89–4.82 (m, 2H), 3.39–3.29 (m, 2H), 3.19–3.09 (m, 2H), 3.06–2.96 (m, 2H), 2.92–2.83 (m, 2H), 2.78–2.68 (m, 2H), 2.34–2.26 (m, 2H) ppm;


13C NMR (150.9 MHz, CDCl3) δ 143.6, 140.2, 139.4, 136.6 (+), 132.9 (+), 131.4 (+), 130.7 (+), 128.8 (+), 48.5 (+), 36.3 (−), 33.3 (−), 27.2 (−) ppm; 


MS (EI, 70 eV) m/z (%): 312 (19), 157 (33), 156 (40), 155 (100), 142 (12), 141 (55), 129 (18), 128 (22), 115 (17).

Interestingly, all three isomers of 10 (trans,trans-, cis,trans- and cis,cis-) under the above irradiation conditions furnish the same product: 16. It is hence likely that a rapid photoequilibration process precedes the ring closure to the final product.

Attempts to crystallize 14 from boiling ethanol led to a mixture of 14 and the cyclooctadiene derivative 15, which was separable by column chromatography. The divinylcyclobutane derivative 14 was completely converted into the cyclooctadiene derivative 15 within half an hour in boiling ethanol. The structure of 15 was confirmed by single-crystal X-ray analysis

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

Henning Hopf1, Vitaly Raev1 and Peter G. Jones2

1Institut für Organische Chemie, Technische Universität Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany, Fax: +49 531 / 391 5388
2Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany, Fax: +49 531 / 391 5387

 Author email       Corresponding author email     

This article is part of the Thematic Series "Photocycloadditions and photorearrangements". Photoactive cyclophanes, part 6. For part 5 see [1].

Guest Editor: A. G. Griesbeck

Beilstein J. Org. Chem. 2011, 7, 658–667.

http://www.beilstein-journals.org/bjoc/single/articleFullText.htm?publicId=1860-5397-7-78


p.jones@tu-bs.de, h.hopf@tu-bs.de


Braunschweig, Germany, 

Braunschweig Alstom LHB GT6 tram no. 8165 at Lincolnsiedlung.

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L-Kynurenine

Table 1. NMR data for the pheromone in CD3OD/D2O

No.	δC	δH	mult(JHz)	COSY	HMBC
1	174.1
2	52.1	4.01	dd(2.7, 9.0)	H-3, 3'	C-1,3,4
3	40.3	3.55	dd( 9.0,18.5)	H-2, 3'	C-1,2,4
3'		3.75	dd(2.7, 18.5)	H-2, 3	C-1,2,4
4	200.3
5	117.7
6	152.8
7	118.4	6.76	d(8.46)	H-8	C-5
8	136.1	7.27	dd(7.12,8.46)	H-7, 9	C-6
9	116.4	6.62	dd(7.12, 8.08)	H-8, 10
10	132	7.74	d(8.08)	H-9	C-4,5,6

mult, multiplicity; d, doublet; dd, double doublet; COSY, correlation spectroscopy; HMBC, heteronuclear multiple bond correlation.

http://en.wikipedia.org/wiki/Kynurenine

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DHAKA BANGLADESH

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Steamers and ferries in Sadarghat Port

Kawran Bazar

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Dry fish sellers at the Karwan Dry Fish Market (Bazar), Dhaka, Bangladesh.

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